prep 一道DS 求解

promiselu

10.    672-!-item-!-187;#058&000324
Juan bought some paperback books that cost $8 each and some hardcover books that cost $25 each.  If Juan bought more than 10 paperback books, how many hardcover books did he buy?

(1)  The total cost of the hardcover books that Juan bought was at least $150.

(2)  The total cost of all the books that Juan bought was less than $260.
--------------------------------------------------------------------------------------------------------------------------------------------------------
【答案】C
【思路】
設paperback = p, hardcover=h,題目問 if P>10, h=?

1+2合起来，P=11，12，13时，H=7。P=14时，H=6。
所以完全不能确定 应该选E  
XDJM你们说答案怎么是C呢？？

shynic89

P=14时，H=6。

cost of P=140
less than 260
260-140=120
但是cost of h最少是150，你这个假设和题目矛盾了。

dolphin_2214

1+2--可以确定P=11，12，13时，H=7
（1）H>6
(2)33H<340 ,即 H<10

promiselu

没人做过这题吗  prep第10题的~