Step 1: Start with the fraction 21/15.

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

21 ÷ 15 = 1.4

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

1.4 × 100 = 140.0%

Final Answer: 21/15 as a percentage is 140.0%.