GWD 17-13

[DARY]

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

Ans: C

我不知道是不是鬼擋牆了,怎麼算都算不出答案來, 拜託版友幫個忙囉!

[zazer.lin]

Juan bought some paperback books that cost $8 each and some hardcover books that cost $25 each. If Juan bought more than(大於,不等於喔!) 10 paperback books, how many hardcover books did he buy?

(1) The total cost of the hardcover books that Juan bought was at least(至少,大於等於喔!) $150
(2) The total cost of all the books that Juan bought was less than(小於,不等於) $260

Ans: C

statement(1) hardcover 至少花掉$150 ==> hardcover > 6本......不充分
statement(2) 所有的書少於$260 .......不充分

合併(1)和(2)
6本hardcover + 11本paperback = 6*25 + 11*8 = 238 < 260
6本hardcover + 12本paperback = 6*25 + 12*8 = 246 < 260
6本hardcover + 13本paperback = 6*25 + 13*8 = 254 < 260

7本hardcover + 11本paperback = 7*25 + 11*8 = 263 > 260

所以hardcover為6本, 故答案(C)

[ariesmilla]

哈囉，你的"大於"和"小於"相反啦....不過解釋的很清楚，THANKS!!
看來我還是欠考慮...SIGN...

[zazer.lin]

哈囉，你的"大於"和"小於"相反啦....

感謝ariesmilla大大的提醒...請容許小弟偷改二樓的回文...

看來早點睡頭腦還是會比較清楚些...

[laca]

不好意思!
我想請問一下至少要花掉150
那不是代表可以花到160.170.180..
那未啥不是買7本8本...........
那這樣不是沒有明確可以買hardcover books!
那這樣不是答案是E
謝謝!

[clbb]

當然可以花160.170

但是paperback books要大於10本 =>至少11本

如果你hardcover books買7本以上 7*25+11*8=263就爆掉了

所以如果有(2)的條件加上(1)就可以解題

--

不過我也有點小問題

為什麼hardcover books 不能買4或5本

4本h+11本p=25*4+8*11=188 , 180<188<260

我是不是哪裡誤會題目了@@??

[waleaaa]

因為條件(1)說─至少花$150買hardcover books
也就是說　hardcover一本$25　所以至少會買6本

[clbb]

哈 謝謝

眼睛都不知道在幹嘛....hardcover books這麼長一條竟然沒看到

[laca]

謝謝!我也是差不多!眼睛有問題!....