Question

4．明明在計(jì)算3×（$\frac{1}{5}$+□）-$\frac{1}{4}$，把括號弄丟了，計(jì)算結(jié)果比正確結(jié)果小了$\frac{1}{3}$，請問□里□應(yīng)該是多少？

Answer 1

分析 根據(jù)題意可得：用原來的算式減去看錯的算式等于$\frac{1}{3}$，列式是：3×（$\frac{1}{5}$+□）-$\frac{1}{4}$-[3×$\frac{1}{5}$+□-$\frac{1}{4}$]=$\frac{1}{3}$，然后解算式即可．

解答 解：3×（$\frac{1}{5}$+□）-$\frac{1}{4}$-[3×$\frac{1}{5}$+□-$\frac{1}{4}$]=$\frac{1}{3}$
                     $\frac{3}{5}$+3□-$\frac{1}{4}$-$\frac{3}{5}$-□+$\frac{1}{4}$=$\frac{1}{3}$
                                          2□=$\frac{1}{3}$
□=$\frac{1}{6}$
答：□里□應(yīng)該是$\frac{1}{6}$．

點(diǎn)評 本題關(guān)鍵是明確運(yùn)算法則，根據(jù)關(guān)系列出算式．