41. 3308-!-item-!-187;#058&003278 Last Thursday, John assembled chairs at a rate of 3 chairs per hour for part of the day and Larry assembled no chairs. Last Friday, Larry assembled chairs at a rate of 4 chairs per hour for part of the day and John assembled no chairs. If John and Larry assembled chairs for a total of 7 hours during these two days, how many chairs did John assemble last Thursday?
(1) During these two days, John and Larry assembled a total of 25 chairs.
(2) During these two days, Larry assembled more chairs than John did. --------------------------------------------------------------------------------------------------------------------------------------------------------【答案】A 【思路】設John用x小時,Larry用y小時 x+y=7 問x=? (1)3x+4y=25 ------------------------------------------------------------------- sufficient (2)4y>3x ---------------------------------------------------------------------insufficient
这边的小，x, y 是整数么， 为什么条件（2）insufficient 呢？ 作者: xiongbaobao 时间: 2010-3-8 15:03
椅子肯定是整数的呀，然后条件就有x=0，y=7或x=1，y=6，或x=2，y=5等几种可能
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