GMAT Quantitative Reasoning Practice Test 1

Since 0.01 and 0.03 each have 2 decimal places, their product must have 4(2 + 2) decimal places. Because 1 × 3 × 5 is 15, you need to add 2 zeros to get the correct number of decimal places, so the product of 0.01, 5 and 0.03 is 0.0015. To change a decimal to a percentage you multiply by 100 and move the decimal point 2 places to the right, so 0.0015 is $0.15\%$.