The phrase “15% of 240” names both required values: 15 is the rate and 240 is the number that supplies the whole. Convert the rate to a fraction of 100, multiply once, and keep the base visible.

Write the percentage as a fraction of 100

15% means 15/100, so the calculation is 240 × 15/100. Exact integer arithmetic gives 3600/100, which reduces to 36.

Check the answer as part of the whole

Divide the result by the base: 36 ÷ 240 × 100 = 15%. This reverse check confirms both the arithmetic and the chosen base. It would fail if 15 and 240 had been swapped.