再请教一道prep上的数学

zoemiaoer

M's recipe for 4 servings of a dish requires 3/2 cups of pasta. according to this recipe, what is the number of cups of pasta that M needs the next time he prepares this dish?
1. the next time he prepares this dish, M will make half as many servings as he did the last time.
2. M used 6 cups of pasta the last time he prepared this dish
我对这个题目的理解是M的食谱是一份4人用量的某菜需要3/2杯的pasta,问按照这个做法，下一次M需要多少杯P
给的第一个条件是M这次做2人用量的这个菜
第二个条件是M上一次做这个菜时用了6杯
此题答案为C
可是我觉得条件一就可以得出结论了，因为一份4人用量的需要3/2的P，那么这次两人用量除以2不就可以了么。觉得选择A
第二个给的条件有什么用么？？
马上要考了 拜托大家给看看吧 谢谢啦！！！！

daicyxy

last time, 他不一定做了4人份的

zoemiaoer

last time, 他不一定做了4人份的

-- by 会员 daicyxy (2010/4/20 0:03:11)

就是说last time他用了6cup,而4人用量为3/2cup,所以退出M 上次是做了4人量【6除以3/2得到】，所以暗示这一次M还是做得4人用量的是么？谢谢~~

daicyxy

设x 为servings of last time,
4 servings requires 3/2 cups, x servings requires 6 cups.
4 : (3/2) = x : 6
所以，  x =  16

next time, M will make half as many servings as he did the last time.
thus, next time, 8 servings
thus, 3 cups of pasta

但是你不需要算出答案，只要判断是否能通过这些条件得出唯一的值。Hope it helps.

zoemiaoer

设x 为servings of last time,
4 servings requires 3/2 cups, x servings requires 6 cups.
4 : (3/2) = x : 6
所以，  x =  16

next time, M will make half as many servings as he did the last time.
thus, next time, 8 servings
thus, 3 cups of pasta

但是你不需要算出答案，只要判断是否能通过这些条件得出唯一的值。Hope it helps.

-- by 会员 daicyxy (2010/4/20 0:19:49)

嗯 是，谢谢了，很感谢！