GMAT Quantitative Reasoning Practice Test 1

Start with the money she had left and work backwards. If she had $\mathrm{\$}5$ left over, and had just spent three-fourths of her money on food, then $\mathrm{\$}5$ must be one-fourth of her money. Before buying food she must have had $5\times 4=\mathrm{\$}20$ . She then spent half of her money on clothes; therefore, $\mathrm{\$}20$ was half of her money, giving her $\mathrm{\$}40$ at this point. She then spent one-third of her money on books and had $\mathrm{\$}40$ left over. If $\mathrm{\$}40$ represents two-thirds of her money, then $\mathrm{\$}60$ must be the amount she began with.