[email protected] wrote:Just want to know what is mean when we write 10!+20, I man how do u simply this?

Thanks

10! + 20 = (10)(9)(8)..(3)(2)(1) + 20

The GMAT would never require you to actually evaluate this (too many tedious calculations)

Cheers,
Brent

[email protected] wrote:How many numbers from 10! to 10!+20 inclusive, are divisible by 3?

NOTE: I reworded the question to avoid ambiguity.

There's a nice rule that says: If M is divisible by k, and N is divisible by k, then (M + N) is divisible by k.

First, since 10! = (10)(9)(8)..(3)(2)(1), we know that 10! is divisible by 3.

So, by the above rule, we know that 10! + 3 is divisible by 3
And 10! + 6 is divisible by 3
10! + 9 is divisible by 3
10! + 12 is divisible by 3
10! + 15 is divisible by 3
10! + 18 is divisible by 3

So, there are 7 integers from 10! to 10! + 20 inclusive that are divisible by 3.

Cheers,
Brent