Q30:
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.
答案是D.
答案有没有问题啊?我觉得 should be C ...
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我也是选的C, 而且没想通正确答案是怎么结出来的
2绝对不能单独解出题目的,答案肯定错了,1还有可能
(1)成立的原因:设两种邮票张数为x和y,则有0.15x+0.29y=4.40。因为邮票的张数x和y只能是整数(这是一个隐含条件),又因为0.15+0.29=0.44,所以能满足这个条件的x,y只能=10,因此(1)单独成立。
(2)应该不可以单独解出.
我选A
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