Question

find the sum of all three digit natural numbers which are divisible by 3 and not divisible by 6

Answer 1

105, 111, 117.........999

a= 105
d = 6

Tn = 999
=> a + (n-1) d = 999
=> 105 + (n-1) 6 = 999
=> (n-1) 6 = 999 - 105
=> (n-1) *6 = 894
=> (n-1) = 149
=> n = 150

Sn = n[ a + Tn] /2
= 150(105 + 999) / 2
= 75 * 1104
= 82800

Sum of all three digit no. which are divisible by 3 but not by 6 is 82800

Answer 2

Step-by-step explanation:

sum of all three digit natural numbers which are divisible by 3 and not divisible by 6 is 82,800