Question:
My son is in 5th grade, he has a math problem. There is three digit number, which is greater than 500, can be divided by 7,9 and 11, but cannot be divided by 2,4,6, and 5. Can you help us to solve this problem? Thanks.

Since the required number is divisible by 7, 9, and 11 it must be divisible by 7x9x11 = 693. I think the key to this problem is the word "and" in the second list of numbers, that is "cannot be divided by 2,4,6, AND 5". 2x396 = 792 is divisible by 7, 9, and 11 but it is not divisible by 2,4,6, AND 5 since it is not divisible by 5.