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Do the ratios form a proportion?

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? $\frac{5}{3}$ and $\frac{25}{15}$

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

 5 × 15 ? = 3 ×25 75 = 75

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

Do these ratios form a proportion? 2 to 5 and 4 to 6

Write the ratios as fractions: $\frac{2}{5}$ and $\frac{4}{6}$

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

 2×6 ? = 5 × 4 12 ≠ 20

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