[讨论]又是两道prep math 请教了

1> if there are more than two numbers in a certain list ,is each of the numbers in the list equal to 0? 

1,the product of any two number in the list is equal to 0

2, the sum of any two numbers in the list is equal to 0

答案给的是B  但是我觉得1 也是对的啊 想不明白 哪位大侠给我解释一下

2》alice's take-home pay last year was same each month. and she saved the same fraction of her take-home pay each month .the total amount of money that she had saved at the end of the year was 3 times the amount of that protion of her monthly take-home pay that she did not saved. if all the money that she saved last year was from her take-home pay, what fraction of her take-home pay did she save each month?

答案是 1/5   也请帮我解释一下 谢谢了

1> 1，存在这样的列{只有一个数不是0，其它数全是零。}

2> 假设，Alice每工资为a元，他每个月储存的部分占工资的比率为x，

   那么Alice每个月储存ax元，没有储存的为 a - ax 元。

   如题所述，有12ax = 3 ( a - ax )

   整理得：x = 1/5

呵呵 谢谢了 我明白了

第1题的解释不对吧，the product of any two number in the list is equal to 0不应该包括只有一个数不是0，其它数全是零的情况，否则就不是any two number in the list了