In solving a/b = c/d, what is cross-multiplication?

In solving a/b = c/d, what is cross-multiplication?

• A. ad = bc
• B. a/b = c/d
• C. a × b = c × d
• D. a/d = b/c

Answer: (A)

Cross-multiplication checks equality of two fractions by clearing denominators. If a/b = c/d with nonzero b and d, multiply both sides by bd to get ad = bc. In other words, the product of the outer terms equals the product of the inner terms. For example, 2/3 = 4/6, and cross-multiplying gives 2×6 = 3×4, both equal to 12.

Cross-multiplication checks equality of two fractions by clearing denominators. If a/b = c/d with nonzero b and d, multiply both sides by bd to get ad = bc. In other words, the product of the outer terms equals the product of the inner terms. For example, 2/3 = 4/6, and cross-multiplying gives 2×6 = 3×4, both equal to 12.