Question

Prove that only one number n-1,n+1,n+5 is divisible by 3

Answer 1

Given numbers,
n-1,n+1 and n+5

Put n = 1,
n-1 = 1-1 = 0
n+1 = 1+1 = 2
n+5 = 1+5 = 6 is divisible by 3

Put n = 2,
n-1 = 2-1 = 1
n+1 = 2+1 = 3 is divisible by 3
n+5 = 2+5 = 7

So, one and only one out of n-1, n+1 and n+5 is divisible by 3.

Hence proved

Answer 2

We have no. Like n-1,n+1,n+5.
Put n=1
n-1=1-1=0
n+1=1+1=2
n+5=1+5=6
So six is divisible by 3
So we can say that only one no. Is divisible by 3



Henced proved