If a ratio a:b = 3:4 and the total parts equal 21, how many parts does b represent?

If a ratio a:b = 3:4 and the total parts equal 21, how many parts does b represent?

• A. 12
• B. 9
• C. 7
• D. 14

Answer: (A)

In a ratio, the total is split into as many parts as the sum of the ratio numbers. Here, a and b occupy 3 parts and 4 parts, totaling 7 parts. The whole is 21 parts, so each part is 21 ÷ 7 = 3 units. Since b corresponds to 4 parts, its amount is 4 × 3 = 12. Therefore, b represents 12 parts.

In a ratio, the total is split into as many parts as the sum of the ratio numbers. Here, a and b occupy 3 parts and 4 parts, totaling 7 parts. The whole is 21 parts, so each part is 21 ÷ 7 = 3 units. Since b corresponds to 4 parts, its amount is 4 × 3 = 12. Therefore, b represents 12 parts.