Step 1: Start with the fraction 21/30.

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

21 ÷ 30 = 0.7

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

0.7 × 100 = 70.0%

Final Answer: 21/30 as a percentage is 70.0%.