Question

5．甲、乙、丙三個(gè)筑路隊(duì)合修一條公路，甲隊(duì)7天修的米數(shù)與丙隊(duì)8天修的相等，甲隊(duì)6天修的米數(shù)與乙隊(duì)5天修的相等，已知丙隊(duì)比乙隊(duì)每天少修$\frac{13}{10}$千米，丙隊(duì)每天修3.5千米．

Answer 1

分析 由于完成相同的工作量，所用時(shí)間與工作效率成反比，甲隊(duì)7天修的米數(shù)與丙隊(duì)8天修的相等，所以丙隊(duì)的效率是甲隊(duì)的$\frac{7}{8}$，甲隊(duì)6天修的米數(shù)與乙隊(duì)5天修的相等，則乙隊(duì)的效率是甲隊(duì)的$\frac{6}{5}$，則丙隊(duì)每天比乙隊(duì)少修了甲隊(duì)的$\frac{6}{5}$-$\frac{7}{8}$，丙隊(duì)比乙隊(duì)每天少修$\frac{13}{10}$千米，根據(jù)分?jǐn)?shù)除法的意義，甲隊(duì)每天修$\frac{13}{10}$÷（$\frac{6}{5}$-$\frac{7}{8}$）米，然后根據(jù)分?jǐn)?shù)乘法的意義求出丙隊(duì)每天修多少千米．

解答 解：$\frac{13}{10}$÷（$\frac{6}{5}$-$\frac{7}{8}$）
=$\frac{13}{10}$÷$\frac{13}{40}$
=4（千米）
4×$\frac{7}{8}$=3.5（千米）
答：丙隊(duì)每天修3.5千米．
故答案為：3.5．

點(diǎn)評(píng) 將甲隊(duì)的效率當(dāng)作單位“1”，首先根據(jù)已知條件求出乙隊(duì)與丙隊(duì)的效率與甲隊(duì)的效率比是完成本題的關(guān)鍵．