Since 0.05 and 0.05 each have 2 decimal places, their product must have 4(2+2) decimal places. Because 5×5 is 25, you need to add 2 zeros to get the correct number of decimal places, so the product of 0.05 and 0.05 is 0.0025. To change a decimal to a percentage you multiply by 100 by moving the decimal point 2 places to the right, so 0.0025 is 0.25%.