Step 1: Start with the fraction 21/24.

Step 2: To convert a fraction into a percentage, divide the numerator by the denominator.

21 ÷ 24 = 0.875

Step 3: Multiply the result by 100 to get the percentage.

0.875 × 100 = 87.5%

Final Answer: 21/24 as a percentage is 87.5%.