求助一道prep数学题，请各位大牛帮忙了，谢谢

zihan_1213

Last Friday each of the pets at a certain veterinary clinic was given either 1 treat or 2 treats.  What was the total number of treats given to pets at the clinic last Friday?

(1) The total number of pets at the clinic last Friday was 90.

(2) 2/3 （三分之二）of the pets at the clinic last Friday were given 2 treats each.

看了解释，明白第一个条件是insufficient，2不太懂，各位明白的教一下我吧，谢谢了

好心情

Last Friday each of the pets at a certain veterinary clinic was given either 1 treat or 2 treats.  What was the total number of treats given to pets at the clinic last Friday?

(1) The total number of pets at the clinic last Friday was 90.

(2) 2/3 （三分之二）of the pets at the clinic last Friday were given 2 treats each.

看了解释，明白第一个条件是insufficient，2不太懂，各位明白的教一下我吧，谢谢了

-- by 会员 zihan_1213 (2010/8/5 10:37:59)

我觉得第二个条件的意思就是有2/3的宠物接受了两种treat。
而且单独第二个条件也不可以因为不知道一共有多少宠物。如果两个条件合起来就可以了，因为2/3的宠物即60只是有two treats，1/3即30只是one treat，所以总共要60*2+30*1=150treats

我觉得是C不知道答案是不是这样哈。。

foreverdr

这。。
2说的是 2/3的pets得到了2 treats
1+2得
90*1/3*1+90*2/3*2=total number of treats given to pets
因为是either or 所以把全集都说出来了 不是给2就是给1。。

zihan_1213

恩，谢谢啦，是这样的。答案就是C

zihan_1213

[quote]
这。。
2说的是 2/3的pets得到了2 treats
1+2得
90*1/3*1+90*2/3*2=total number of treats given to pets
因为是either or 所以把全集都说出来了 不是给2就是给1。。

-- by 会员 foreverdr (2010/8/5 10:46:49)

谢谢楼上的童鞋，是这样的，灰常感谢