Question

1．甲、乙、丙三個(gè)修路隊(duì)合修一條公路，甲隊(duì)修了全長(zhǎng)的40%，乙隊(duì)修了剩下的75%，丙隊(duì)修了9千米正好修完．這條公路全長(zhǎng)多少米？乙隊(duì)比甲隊(duì)多修了百分之幾？

Answer 1

分析 由“甲隊(duì)修了全長(zhǎng)的40%，乙隊(duì)修了剩下的75%，”可以求出乙隊(duì)修了全長(zhǎng)的（1-40%）×75%，進(jìn)一步求出丙隊(duì)修了9千米正好是全長(zhǎng)的[1-75%-（1-40%）×75%]，根據(jù)分?jǐn)?shù)除法的意義列式解答即可．
用這條公路的全長(zhǎng)減甲隊(duì)修的，再減丙隊(duì)修的，即可得乙隊(duì)修的千米數(shù)，減甲隊(duì)修的千米數(shù)，再除以甲隊(duì)修的千米數(shù)即可．

解答 解：9÷[1-40%-（1-40%）×75%]
=9÷[1-0.40-0.45]
=9÷0.15
=60（千米）；
（60-60×40%-9-60×40%）÷60×40%
=（60-24-9-24）÷24
=3÷24
=12.5%，
答：這條公路全長(zhǎng)60千米；乙隊(duì)比甲隊(duì)多修了12.5%．

點(diǎn)評(píng) 解答此題關(guān)鍵求出乙隊(duì)修了全長(zhǎng)的百分之幾，再進(jìn)一步根據(jù)全長(zhǎng)-甲乙兩隊(duì)修的=丙隊(duì)修的列式解答即可．