Charlie watched 1/2 of a movie in the morning, and he watched some more at night. By the end of the day, he still had 1/5 of the movie left to watch. How much of the movie did Charlie watch at night?

lmk if u want a more detailed explanation but since it's urgent here's the answer.

Step-by-step explanation:

(n^3 - n)

= n(n-1)(n+1)

since it is divisible by 3 and 2 ,because it is a multiple 3 consecutive number

if, n-1 is odd then n+1 is also odd, then it is a multiple of 9

but if, n-1 is even then n+1 is also even, then it is a multiple of 4

so, largest multiple = max(9*2, 4*3) = max(18, 12) = 18