Step 1: Start with the fraction 21/70.

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

21 ÷ 70 = 0.3

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

0.3 × 100 = 30.0%

Final Answer: 21/70 as a percentage is 30.0%.