Math Useful

Multiply by 15 Shortcut

Multiplying by 15 requires multiple steps with traditional methods. Multiply by 10, then add half of that result.

Problem

Multiplying by 15 requires multiple steps with traditional methods.

Solution

Multiply by 10, then add half of that result.

Benefit

Reduces complex multiplication to simple addition.

Example 

24 × 15:
24 × 10 = 240
240 ÷ 2 = 120
240 + 120 = 360

36 × 15:
36 × 10 = 360
360 ÷ 2 = 180
360 + 180 = 540
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