Fill in three of the four values and leave the unknown one empty.
Leave the unknown one empty.
Missing value12
Completed proportion3/4 = 9/12
Cross products (a × d = b × c)36 = 36
Value of each ratio0.75

Cross-multiply: a × d = b × c → 4 × 9 = 36 → d = 36 ÷ 3 = 12.

Proportion Calculator · free calculator by CalcWorthy