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Do the ratios form a proportion: word problems

A proportion is a statement that two ratios are equivalent to each other. Two ratios form a proportion if their cross products are equal.

Do these ratios form a proportion?

Tony swims 10 laps in 30 minutes.
Rogert swims 15 laps in 45 minute.

Write the ratios as fractions. and

Compare the two cross products. Multiply the numerator of one fraction and the denominator of the other.

 10 × 45 ? = 15 ×30 450 = 450

The cross products are equal, so the ratios form a proportion
.

Do these ratios form a proportion?

Tony reads a 120-page book in 4 hours.
Rogert reads a 160-page book in 5 hours.

Write the ratios as fractions. and

Compare the two cross products. Multiply the numerator of one fraction and the denominator of the other.

 120 ×5 ? = 150 × 4 600 ≠ 640

The cross products are not equal, so the ratios do not form a proportion.