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答案没有解释,不知道怎么算的,请教大家啦 1.Candy hears were marked down from 30%to 50% on Valentines's Day. The following day, candy hearts were marked down an additional 25%. What was the lowest cost of a candy heart that originally sold for 28$? 答案是$7,我算的是28*0.5*0.75 2.Jerome wrote each of the intergers 1 through 20, inclusive, on a separate index card. He placed the cards in a box, then drew cards one at a time randomly from the box, without returning the cards he had already drawn to the box. In order to ensure that the sum of all the cards he drew was even, how many cards did Jerome have to draw? 答案是19,我百思不得其解 3.What is the value of the sum of a sequence of three consecutive even integers? (1)The average of the gree consecutive even integers is 14 (2) The product of the smallest and largest is 192 答案是D.但是如果考虑负整数的情况(2)是不能确定的啊,可以是12,14,16,也可以是-16,-14,-12 4.A home owner must pick between paint A , which costs $6 per liter, and paint B, which cost $4.5 per liter. Paint B takes one-third longer to apply than Paint A. I fth ehome owner must pay the cost of labot at the rate of $36 per hour, which of the two paints will be cheaper to apply? (1) The ratio of the area are covered by one liter of paint A to the area covered by B is 4:3. (2) Paint A will require 40 liters of paint and 100 hours of labor. 答案是E. 我这样算,不知道问题在哪里.设A, B 分别用a liters,b liters, t1 hours, t2 hours 对于(1), a:b=3:4, A的总费用=a*6+ t1*36 B的总费用=b*4.5+t2*36=6a+48*t1>A 是不是因为我把Paint B takes one-third longer to apply than Paint A.这句话理解错了呢,不是t2=4t1/3的意思吗 | 
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发表于 2008-7-27 09:41:00
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