How to Tell If Fractions Are Proportionate

Comparing Two Fractions

• 1

  Examine the equation 2/5 = 8/20. Are they proportionate?

• 2

  Multiply the first fraction by 4: 2 x 4 = 8 and 5 x 4 = 20. Therefore, 2/5 is equal to 8/20.

• 3

  Compare the two fractions: 15/125 = 3/25. Are they proportionate?

• 4

  Cross multiply the parts of the fraction: 15 x 25 = 375 and 125 x 3 = 375. Because both fractions have a cross-product of 375, they are equal.

Using Variables and Ratio Comparisons

• 5

  Read the following problem: "If it takes Jim 6 minutes to burn 15 songs, how long will it take him to burn 20?"

• 6

  Set up a ratio as a fractional equation with the required information: 6/15 = x/20

• 7

  Cross multiply the parts of the fractions: 6 x 20 = 120 and 15 x (x) = 15x.

• 8

  Set the two products equal to each other: 120 = 15x.

• 9

  Divide both parts of the equation by 15: 120 ÷ 15 = 8 and 15x ÷ 15 = x. Therefore, it would take Jim 8 minutes to burn 20 songs: 6/15 = 8/20.