# Hot Math Posts

### How To: Find a data point (Xi) with the Z-Score formula

In this free video math tutorial, we learn how to use the Z-Score formula to find a data point (Xi) in statistics. With mathematics, as with anything else, not everyone progresses at the same rate. Stats is no exception. Happily, in the age of Internet video tutorials, this isn't a problem. Those who progress quickly can go beyond what's being taught them and those who are struggling likewise have all the time in the world to catch up. Whether you need help finishing your homework or studying...

### How To: Prove Rank(A) = Rank(transpose of A) in linear algebra

Learn how to prove that the rank of a matrix, A, is equal to the rank of its transpose in linear algebra. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

### How To: Find the equation of an ellipse given a graph

Notes College Algebra teaches you how to find the equation of an ellipse given a graph. You first want to find out the center of the ellipse, which in the video is (2, -3). The major axis is parallel to the X axis. The equation is (x - h) squared/a squared plus (y - k) squared/a squared equals 1. A is the distance from the center to either of the vertices, which is 5 over here. B is the distance from the center to the top or bottom of the ellipse, which is 3. You then use these values to find...

### How To: Subtract fractions with borrowing

This how-to video describes how to subtract fractions using the borrowing method. The video shows viewers everything they need to know including basic subtraction of fractions, how to find common denominators, to the more difficult borrowing techniques. The narrator in this video does a great job of keeping things simple enough for anybody to understand. At the same time, he goes in depth enough that you really get how to use this technique. The voice in this video is very calm and clear. Thi...

### How To: Use a mean and scatter plot for Statistics

Wondering how to use a mean and scatter plot for statistics? Just follow the few simple steps as below.

### How To: Simplify complex fractions with variables

In order to simplify complex variables, you must first consider the numerical values separate from the variable. In the case of 24x/48x, you would look at the numbers alone to see if they have any factors. These numbers have the number 6 in common. So, divide it by 6. This will give you 4/8. This still requires some simplification. Two is still a factor for both. So, divide it again by four. This will give you 1/2. Now, if the numerator was raised to the second power, in the original equation...

### How To: Find X-bar with the Z-score formula

In this video tutorial it shows you how to find the x-bar by using the Z-score formula. In the beginning of this video the formula is displayed on the right, while the values that you need to plug in are on the left. Once you plug in the values and do the cross multiplying, all you have to do is get x-bar by itself on one side of the equation. This is a simple problem on using the z-score formula to find x-bar, it can help you solve more complex problems in the future.

### How To: Clear decimals from a linear equation

Need instructions on how to remove decimal values from a linear equation in algebra? Learn how with this free video lesson. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

### How To: Derive the equation of a straight line

In this tutorial the instructor shows how to derive a straight line equation. He shows us a process that consists of two steps. In step one he uses the slope formula to obtain the slope of the line which is the ratio of difference of y-coordinates and difference of x-coordinates. Now in the step two he uses the slope he obtained in the first step and equates it two a another slope derivation which uses a generic x, y variables and a real point. Now solving this equation he arrives at the equa...

### How To: Draw a reflection in Geometry

In this tutorial the author shows how to draw reflections in geometry. He shows how to draw them with a couple of examples in which he uses a reflection line and an object whose image is to be reflected. Now he draws perpendicular lines to the reflection line from the vertex of the original figure. He draws similar lines to all the vertexes all of same length and now after joining the ends of those lines a reflection of the original figure is obtained. This video shows a step by step method t...

### How To: Solve angle problems in geometry

Need some help figuring out how to work with angles in geometry? Look no further. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of free math tutorials, you'll learn how to sol...

### How To: Deal with brackets in polynomials

This how-to video shows viewers how to solve math problems with brackets in polynomials. The person in the video teaches people how to solve the problem with a positive sign before the brackets. This segment does not show how to solve the trickier problem where there is a negative sign in front of the brackets. The tutor shows everything from removing the bracket due to the positive sign, to combining the similar terms for the result of the problem. This video can help anybody deal with brack...

### How To: Solve quadratic equation word problems in algebra

Need help figuring out how to unpack and solve word problems involving quadratic equations? Learn how with this free video algebra lesson. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

### How To: Use probability to predict weather

In this video, we learn how to use probability to predict weather. Probability is the chance of something happening. If you want to know what the weather is going to be like, you can look at the weather report and see what each day is going to do throughout the week. Ask yourself what the probability is that the weather will be cloudy, judging from what the current work week weather is. First, figure out how many days there are total and then find out how many are cloudy versus how many are s...

### How To: Find the volume of a cylinder quickly

In this video the tutor shows how to find the volume of a cylinder. He relates the cylinder to real world examples of cans etc. Now he states the formula of the volume of the cylinder as the area of the base circle multiplied by the height of the cylinder. So the formula turns out to be V = Pi * r * r * h, where r is the radius of the base circle and h is the height of the cylinder. He solves a sample example to give you the idea of the problem. This video shows you how to find out the volume...

### How To: Simplify exponential expressions in basic algebra

The video shows how to solved mixed property problems using the exponent rules. See if there are any rules you can apply to the problem until you get to a point where you can't simplify anymore. The instructor shows in the example problem that the two bases are the same, but there is extras happening the numerator. The power to power multiply rule is applied removing the extra issues from the numerator. Next the quotient rules is applied as there is the exact same base to the power so we keep...

### How To: Find the perimeter of a shape

Two dimensional objects are measured in terms of perimeter and areas. A perimeter of a two dimensional object is the distance around that object. If you want to find the perimeter of an object, all you need to do is add up each one of the lengths of sides of that object. If you have a small figure like triangle, first compute the length of the three sides. Now adding these three sides gives you the perimeter of the triangle. A larger or more complicated shape might have more number of sides. ...

### How To: Solve problems involving functions in algebra

Need to know how to solve function problems in algebra? From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of free math tutorials, you'll learn how to work with and solve functions.

### How To: Solve linear equations in the form of AX+B=C

Need to know how to solve AX+B=C-form linear equations in algebra? From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of free math tutorials, you'll learn a system for solving line...

### How To: Subtract positive & negative numbers

In this Math Made Easy tutorial the author shows how to subtract positive and negative numbers. He says that because of the numerous combination of positive and negative numbers it adds to a lot of confusion. Now he shows a trick of how to add positive numbers to negative numbers showing that it's equivalent to subtracting the negative number from the positive number. He shows that if you want to subtract a negative number from a positive number we should actually cancel all the signs and the...

### How To: Calculate the age of the universe w/ Hubble's constant

This is a great instructional video on how to calculate the age of Universe from Hubble's constant. The speed the galaxy moves away from us is directly proportional to the distance from us. Now think of big bang theory. Hubble's constant is equal to velocity over distance. 1 over Hubble's constant is equal to distance over velocity that is equal to time. Time equals to 1over 71. If you change it into all the same units words it is one over 71000 or 3.09x 10 to the power of 22. It is 3.09x10 t...

### How To: Solve basic linear function word problems in algebra

Need some help solving linear function word problems? See how it's done with this free video math lesson. Need help finding the From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series o...

### How To: Interpret derivatives of marginal cost and revenue

This video tells us the method of interpreting derivatives of marginal cost and revenue. If C(x) is the cost of producing x units of a product, C(400) would be the cost to produce 400 units. Now marginal cost is the cost of producing one unit which is equal to the derivative of the cost function or C'(400) which is equal to limit of h tends to zero or lim h->0 [lim(400+h)-lim(400)]/h which is approximately equal to [lim(401)-lim(400)]/1. Similarly, if R(x) is your revenue function, marginal r...

### How To: Find real and imaginary parts of a complex number

Need a little help with your math homework? No problem, the Math Centre offers students video tutorials that will provide as a reference guide for self-study. Students get self-study resources targeted to the needs of individual courses, and teachers gain generic mathematics support and study materials for use with students.

### How To: Express big & small numbers with scientific notation

See how to express very large and very small numbers using scientific notation with this free video math lesson from Internet pedagogical superstar Simon Khan. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

### How To: Solve simple algebraic equations

This is a great series of videos showing you how to solve simple algebraic equations. The first video demonstrates solving equations using addition or subtraction, the second deals with solving equations using multiplication or division, and the third shows how to solve multistep equations.

### How To: Find points on y-axis a certain distance from a point

This is video on mathematics. It specifically deals with geometry. The video describes how to determine where the y-intersects are when a point and distance to the y-intersect are given. The author starts out by giving an example ordered pair. The speaker next shows an example of how to solve such a problem. The speaker uses the distance formula along with the given distance and x-coordinate in order to solve for the y-intersect values in question. Most of the video entails solving this example.

### How To: Solve problems involving deductive reasoning

From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of free math tutorials, you'll learn how to unpack and solve word problems that require you to apply deductive reasoning.

### How To: Solve rational equations easily

This video revolves around solving rational equations in Algebra 2. When you are given a rational equation, you have to find the greatest common factor and multiply all fractions to get that common factor. If a fraction already has that common factor, then no further step is necessary for that one. Next, you have to multiply all fractions by the greatest common factor to get rid of all denominators. Finally, the remaining equation is simple math and you only need to solve the equation for the...

### How To: Subtract numbers on an abacus calculator

Lawrence Perez, from Saddleback College, and his assistant Charlie, give this two-part arithmetic lesson on subtracting with an abacus. Could this be any easier than adding? Maybe, can you "borrow" the knowledge to subtract these numbers without an electric calculator? See for yourself.

### How To: Find the equation of trig functions by their graphs

Need to know how to determine the equations of trigonmetric functions by inspecting their graphs? Learn how. Learn how to use trigonometric functions to calculate the sides of a right triangle. Need to know how to solve a matrix-form linear equation in algebra? From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just f...

### How To: Use the distance formula for two points

In this tutorial, we learn how to use the distance formula for two points. The distance formula is D= the square root of (X2-X1) squared, plus (Y2 minus Y1) squared. It may look confusing, but it's just a derivation of a theorem. First, find the two points that you have and graph them. If you want to know the distance between them, you cannot just count squares if it's a diagonal line. If you remember geometry, you can draw a right triangle over the line to figure out the distance. After this...

### How To: Evaluate a telescoping series using partial fractions

Looking for a primer on how to solve a telescoping series using partial fractions? See how it's done with this free video college algebra lesson. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

### How To: Simplify square roots in algebra

Watch the following video to understand the steps necessary when simplifying square roots. To simplify expressions with radicals, follow these simple steps:

### How To: Compute a square root using the geometric method

With mathematics, as with anything else, not everyone progresses at the same rate. Happily, in the age of Internet video tutorials, this isn't a problem. Those who progress quickly can go beyond what's being taught them and those who are struggling likewise have all the time in the world to catch up. With this free video math lesson, you'll learn how to calculate the value of a square using using geometry.

### How To: Understand binary numbers in 60 seconds

Understand how binary numbers work, including how to read binary numbers, and create your own. This mathematics or computer programming tutorial is a zip to get through. It covers practical and theoretical use and need for binary code understanding. Binary means zeroes and ones in a series. This is paramount to digital transmission versus analog that transmits in a sinusodial wave form.

### How To: Find the area of a ring w/ the areas of 2 circles

Doina Popovici's video explains how to calculate the area of a ring. She takes us really slow, down to all the steps of this process. It's very important that she explains every math formula and operation so you cannot get lost into this solving. The video uses nice pictures and colors in order to make learning easier and nicer for those who are interested. At the end of the video you'll surely be able to solve by yourself a problem like that and your appetite for geometry will grow significa...

### News: Encrypting Passwords With an Old-School Tabula Recta

Have an old-school tabula recta lying around? No? Then just print out the chart below. Nothing ensures better password security than this centuries-old cipher technique. Here's how it works, via Wikipedia:

### How To: Subtract positive and negative integers

How to subtract positive and negative integers: There are four types of subtraction:

### How To: Multiply three digit numbers in a single step

Want to be able to do large multiplication problems without a calculator? This video will teach you a method of multiplication in which you will be able to multiply three digit numbers in a single step. Multiply three digit numbers in a single step.