Question

find the sum of all three digit natural numbers which are divisible by 13

plz answer

Answer 1

a = 104 an = 988

an = a+(n-1)d

988 = 104+(n-1)13

988 - 104 = (n-1)13

884/13 = n-1

68+1 = n

n = 69

sn = 69/2(104 + 988)

sn = 69/2*1102 = 551*69

sn= 38019