prep2 ds-158,200

A store purchased 20 coats that each cost an equal amount and then sold each of the 20 coats at an equal price.  What was the store's gross profit on the 20 coats?

(1)  If the selling price per coat had been twice as much, the store's gross profit on the 20 coats would have been $2,400.

(2)  If the selling price per coat had been $2 more, the store's gross profit on the 20 coats would have been $440.

答案是B

200.
                        19224-!-item-!-187;#058&012506

If d is a positive integer and f is the product of the first 30 positive integers, what is the value of d ?

(1) 10^d is a factor of f.

(2) d > 6

答案是C

请帮忙解答一下，谢谢。

第一个问题是:一个商店进货了20件外套,每件外套的进货价格相同,然后又以相同的价格出售.问商店的毛利是多少?

设出售的单价为p/件,成本为c/件,列出公式就是20p-20c=gross profit;

(1)如果每件外套以2p的价格出售,则gross profit=2,400,即2*20p-20c=2,400,不能求出20p-20c=多少

(2)如果每件外套以p+2的价格出售,则gross profit=440,即20*（p+2）-20c=440,即20p-20c=440-20*2=400=gross profit

所以B

第二题我也不明白~~~关注中

第二个问题

1）可以推出，d可以是1，2，3，4，5，6，7

前三十个正整数的积可以质因数分解为几个5

5*10*15*20*25*30一共是7个5

2）d>6

所以两个条件满足后得出d=7

不好意思，表达能力比较差。。。LZ凑合着看下

明白了，谢谢大家了。