求助！一道GWD数学

sarahzhensh

A definitely

iamataker

我认为答案是A，

4楼那位的解答看似有点道理 ，但那个方程列的有问题。

为什么等号左边是4.4 ？题目哪里告诉你4.4了？其实是第一个选项说总共买了4.4元邮票的 ，而不是题目啊！所以单单第二个条件是不可能推出答案的 ，可能买了1000张而每种各买了500呢？

jh1904

Condition 1 and 2 have to be considered independently! Only when both are not sufficient independently then we consider whether 1 plus 2 are efficient.

In this question, 1 alone is sufficient. 2 alone is not sufficient as Joanna can buy 2, 4, 6, 8, ...........20000000 stamps. You may argue that but with condition 1, there can only be 10 stamps. Well, 1, by  itself, is sufficient. 2 alone is not sufficient, so the answer is A.

rimm853

It looks like the answer is D rather than A

yqqlmgsycl

(1)=>0.15X+0.29Y=4.4 => 15X + 29Y = 440 => X<=29 & Y<=15.

Y can only be 5, 10, or 15 to make the digit unit of 29Y equal to 0 or 5.  With Y=5 or 15, X is not integer.  So Y=10, X=10.

lucifer2045

(2)
          She bought an equal number of $0.15 stamps and $0.29 stamps.

4.4=(0.29+0.15)*x

x=10

不是也能解出来吗?

Sophia0703

好奸诈啊！！这题！！谢谢LS!

坚定之路

此题我曾经上当过，答案为A；因为要凑齐4.4元，只能是10张0.15元和10张0.29元，别无他法。

Sophia0703

Joanna bought only $0.15 stamps and $0.29 stamps.  How many $0.15 stamps did she buy?

(1)
          She bought $4.40 worth of stamps.

(2)
          She bought an equal number of $0.15 stamps and $0.29 stamps.