Question

how many three digit numbers are divisible by 3

Answer 1

3 is divisible when the numbers that we add is divisible by 3 for eg 343 3+4+3=10 which is not divisible by 3

Answer 2

a=102
d=3
l=999

an = a+ (n-1) ×d
999 =102 + (n-1) 3
999-102 =(n-1) 3
879 = (n-1)3
n = 293+1=294