Question

Find the sum of all three digit no. Which are divisible by 3 not by 5

Answer 1

three digit number starts with 100 to 999

divsible by 5= 100, 105, 110, 115, 120, 125, 130..............995

so d= 105-100 = 5 , a = 100, n= 180

so sum = n/2 (2a+ (n-1)d)

90(2*100+179*5)

=98550