Question

How many different ten digit telephone numbers contain four 2's, three 3s, and three 7s?

I tried sorting the numbers out in order

2 2 2 2 | 3 3 3 | 7 7 7

10!/2!3!7!

But I couldn't find the correct solution as the answer was 4200

Answer 1

no, you probably meant
10!/(4!,3!,3!)
= 4200

Answer 2

Let's say
N=10
a=4 2s
b=3 3s
c=3 7s

Therefore, 10!/(4!×3!×3!)=4200

I hope it helps