Multiplying by 25 Trick

To multiply a number by 25, you can think of 25 as $\frac{100}{4}$. The strategy is to divide the number by 4 and then multiply by 100 (or move the decimal two places to the right).

For example, $84 \times 25 = \frac{84}{4} \times 100 = 21 \times 100 = 2100$.

Similarly, to divide by 25, you multiply by 4 and move the decimal two places to the left. For example, $415 \div 25 = \frac{415 \times 4}{100} = \frac{1660}{100} = 16.6$.