prep有两题不懂

dolphin_2214

1.in a certain deck of cards ,each card has a positive integer written on it. in a multiplication game, a child draws a card and multiplies the integer on the card by the next larger integer. if each possible product is between 15 and 200 ,then least and greatest integers on thw cards could be
(1) 3 and 15   (2) 3 and 20 (3) 4 and 13 (4) 4 and 14 (5) 5 and 14
答案是（3）

还有

2
n is multiple of 5 and n=p^2*q,  p,q is prime number, 问哪个是multipul of 25?
答案p^2*Q^2

有人也提出来不懂，我在这也想问~求指教！

快乐小龙

if each possible product is between 15 and 200
卡上的数字N乘上N+1后的结果在15和200之间
先定最小的数字，15=3*5，3不行，4可以，4*5>15
选项3和4可能是答案，然后定最大的数字，13*14<200, 14*15>200
所以是选项3

第二题，n是5的倍数，p^2*q也是5的倍数，P或者Q中一个是5的倍数。确保25的倍数，那么就需要q^2