If the simplified fractions are the same, the proportion is true; if the fractions are different, the proportion is false. To cross multiply, you multiply the numerator of the first ratio in the propo...If the simplified fractions are the same, the proportion is true; if the fractions are different, the proportion is false. To cross multiply, you multiply the numerator of the first ratio in the proportion by the denominator of the other ratio. Then multiply the denominator of the first ratio by the numerator of the second ratio in the proportion. Imagine you want to enlarge a 5-inch by 8-inch photograph to make the length 10 inches and keep the proportion of the width to length the same.
