A family spends 62% of its monthly earnings and puts one-fourth of what is left into a deposit. What per cent of its monthly earnings goes into the deposit?

Take the earnings as 100. Spending takes 62, leaving 38, and a fourth of 38 is 9.5, so 9.5% of the earnings goes into the deposit. 25% takes the fraction on the whole earnings instead of on the leftover. 15.5% is 62/4, quartering the amount SPENT rather than the amount left. 28.5% is three-fourths of 38, the part of the leftover that does NOT go into the deposit.