#### Answer

62.04% carbon, 10.41% hydrogen and 27.55% oxygen.

#### Work Step by Step

Mass percentage of an element =
(mass of that element in the compound × 100)/(molar mass of the compound)
Molar mass of acetone ($C_{3}H_{6}O$) = $(3\times12.011g)+(6\times1.008g)+(1\times15.999g)$ = 58.08 g
Mass % of C = $\frac{(3\times12.011g)\times100}{58.08g}$ = 62.04%
Mass % of H = $\frac{(6\times1.008g)\times100}{58.08g}$ = 10.41%
Mass % of O = $\frac{15.999g\times100}{58.08g}$ = 27.55%