To solve a proportion for a variable you should employ cross multiplication. The basis of cross multiplication is the property which states that the product of the numerator of one fraction and the denominator of what it is set equal to is equal to the product of the remaining denominator and numerator. For example if you have x/15=21/45 you simply need to multiply x by 45 and 15 by 21 then set them equal to each other. The result of this is 45x=315. To solve this new problem for x, divide both sides by 45. The final result of this is x=7. This skill is important for many word and trigonometry problems.
 Hot
 Latest

How To: Remember "greater than" & "less than" symbols

How To: Calculate Faster Than a Calculator

How To: Find the Percent Given Two Numbers

How To: Divide small numbers by big numbers

How To: Use ">" (greater than) and "<" (less than) symbols

How To: Calculate the area of a parallelogram

How To: Find the area of a circle when you know the diameter

How To: Find the formula of a piecewise function given a graph

How To: Calculate probability in "at least one" problems

How To: Use derivatives to find slope in calculus

How To: Solve advanced ratio problems in algebra

How To: Perform an astonishing toothpick math trick

How To: Clear fractions from linear equations in Algebra

How To: Solve reverse percentage problems

How To: Find the sides of a 454590 right triangle

How To: Do long division without a calculator

How To: Find a number given Its percent

How To: Determine the age of a fossil using carbon14

How To: Solve equations with the order of operations

How To: Spend Money on a Graphing Calculator? Nah—Just Use This WebBased TI Emulator

How To: Remember "greater than" & "less than" symbols

How To: Calculate Faster Than a Calculator

How To: Find the Percent Given Two Numbers

How To: Divide small numbers by big numbers

How To: Use ">" (greater than) and "<" (less than) symbols

How To: Calculate the area of a parallelogram

How To: Find the area of a circle when you know the diameter

How To: Find the formula of a piecewise function given a graph

How To: Calculate probability in "at least one" problems

How To: Use derivatives to find slope in calculus

How To: Solve advanced ratio problems in algebra

How To: Perform an astonishing toothpick math trick

How To: Clear fractions from linear equations in Algebra

How To: Solve reverse percentage problems

How To: Find the sides of a 454590 right triangle

How To: Do long division without a calculator

How To: Find a number given Its percent

How To: Determine the age of a fossil using carbon14

How To: Solve equations with the order of operations

How To: Spend Money on a Graphing Calculator? Nah—Just Use This WebBased TI Emulator
Be the First to Comment
Share Your Thoughts