Question

20．甲、乙、丙3個(gè)工程隊(duì)合修一條公路，甲隊(duì)修了全程的40%，乙隊(duì)比丙隊(duì)多修180米，乙隊(duì)與丙隊(duì)修路米數(shù)的比是9：7，這條公路長(zhǎng)多少米．

Answer 1

分析 乙隊(duì)與丙隊(duì)修路米數(shù)的比是9：7，把乙隊(duì)修路米數(shù)看作9份，則丙隊(duì)修路米數(shù)為7份，乙隊(duì)比丙隊(duì)多修9-7=2份，多修180米，用除法可得1份的米數(shù)，再求得乙隊(duì)與丙隊(duì)合修的米數(shù)，甲隊(duì)修了全程的40%，可得乙隊(duì)與丙隊(duì)修了全程的1-40%=60%，用除法即可得這條公路長(zhǎng)多少米．

解答 解：180÷（9-7）×（9+7）÷（1-40%）
=180÷2×16÷60%
=90×16÷60%
=2400（米）
答：這條公路長(zhǎng)2400米．

點(diǎn)評(píng) 本題考查了百分?jǐn)?shù)復(fù)合應(yīng)用題，關(guān)鍵是得出乙隊(duì)與丙隊(duì)合修的米數(shù)．