Question

If 1 + ${\sum }_{r=0}^{18}$ (r(r + 2) + 1) r! = n!, then n is not divisible by

• A. 4
• B. 6
• C. 10
• D. 20

Answer 1

The correct option is B

6

1 + ${\sum }_{r=0}^{18}$ (r(r + 2) + 1) r! = 20! ⇒ n = 20.