Compared to what other are posting, I would like to start

Hallo Kunbol, i can not get what is your answer. is it C) or E)?Thanks

If your answer is C) then , as you have pointed out D=200 and sqrt200<15 but on the other hand 400 is also divisible by 25 and 40 and sqrt400>15. I would go with E)

i guess you are right then..i was thinking of that..but i assumed.....i agree with you..seems to be E
thanks

Thanks Praetorian for your encouraging words. My math skills are very rusty due to long break and I have short time to prepare. I see very smart people posting here with good questions, most of which I cannot answer but I am trying hard to pick lot of stuff in short time.


Official answer is E but in a hurry I picked C after just finding one integer which satisfied the stem(400) but could not figure out there could be more than one satisfying stem. After review of above I would have approached the problem in the following manner.

1. Least integer that can satisfy sqrt(d) > 15 is 16. Thus least d can be 256. Closest integer greater than 256 that is divisible by 25 is 400. Also 10000 satifies and thus insufficient.

2. d is divisible by 40 which again is satisfied by 400 or 10000. Thus insufficient.
Combining still d can be 400 or 10000.
Is there more structured approach to these kind of problems. How much time I need to spend to plug numbers approach vs. more formalized approach which obviously needs better command of numbers theory I guess.