O cuidado está no "dos que sobraram": o $\mathbf{\frac{\textcolor{#ef4444}{2}}{\textcolor{#3b82f6}{3}}}$ do irmão não cai sobre a caixa inteira, e sim sobre o que restou depois de Marina. Primeiro, quanto sobra.

Marina come $\mathbf{\frac{\textcolor{#ef4444}{1}}{\textcolor{#3b82f6}{4}}}$ da caixa, então sobram os outros $\mathbf{\frac{\textcolor{#ef4444}{3}}{\textcolor{#3b82f6}{4}}}$ dos 48:

$\mathbf{\dfrac{\textcolor{#ef4444}{3}}{\textcolor{#3b82f6}{4}} \times \textcolor{#ef4444}{48}}$

= $\mathbf{\dfrac{\textcolor{#ef4444}{3} \times \textcolor{#ef4444}{48}}{\textcolor{#3b82f6}{4} \times \textcolor{#3b82f6}{1}}}$

= $\mathbf{\dfrac{\textcolor{#ef4444}{144}}{\textcolor{#3b82f6}{4}}}$

= 36

Sobraram 36 bombons. Agora o irmão come $\mathbf{\frac{\textcolor{#ef4444}{2}}{\textcolor{#3b82f6}{3}}}$ desses 36:

$\mathbf{\dfrac{\textcolor{#ef4444}{2}}{\textcolor{#3b82f6}{3}} \times \textcolor{#ef4444}{36}}$

= $\mathbf{\dfrac{\textcolor{#ef4444}{2} \times \textcolor{#ef4444}{36}}{\textcolor{#3b82f6}{3} \times \textcolor{#3b82f6}{1}}}$

= $\mathbf{\dfrac{\textcolor{#ef4444}{72}}{\textcolor{#3b82f6}{3}}}$

= 24

Há um atalho pela multiplicação de frações: tomar $\mathbf{\frac{\textcolor{#ef4444}{2}}{\textcolor{#3b82f6}{3}}}$ de $\mathbf{\frac{\textcolor{#ef4444}{3}}{\textcolor{#3b82f6}{4}}}$ da caixa é a conta $\mathbf{\frac{\textcolor{#ef4444}{2}}{\textcolor{#3b82f6}{3}} \times \frac{\textcolor{#ef4444}{3}}{\textcolor{#3b82f6}{4}}}$ , que dá $\mathbf{\frac{\textcolor{#ef4444}{1}}{\textcolor{#3b82f6}{2}}}$ — e a metade de 48 também são 24.

O resultado correto é 24 bombons.

Questão Q14867