If the ratio of rice to wheat is 3 : 4 and rice is 21, then wheat is:

Correct answer: 28. 3 parts = 21, so 1 part = 7, and wheat = 4 × 7 = 28.

Background: First find the value of one part.

• 24: 24 is 4 × 6.
• 26: 26 is not a multiple of 4 parts.
• 30: 30 is not a multiple of 4 parts.

Did you know? 1 part = given value ÷ its ratio number.

Memory trick: 21 ÷ 3 = 7, then × 4.