Question

fiind the sum of all three digit no.s which are divisible by 3 but not by 5​

Answer 1

3*5=15

All the three digit number divisible by 15

AP=105,120,135,,,,,.....,990.

A=105

L=990

990=105+(n-1)15

990-105=(n-1)15

885/15=n-1

59+1=n

n=60.

Sn=60/2*(105+990)

=30*1095

=32850.

Hope it is helpful