Question

5.
Find the sum of all two - digit natural numbers which are divisible by 3.​

Answer 1

1665

Explanation:

This is AP, where:

• First term is: 12= 3*4
• Last term is: 99= 3*33
• Common difference is: 3
• Number of terms is: 33- 3= 30 (because the 4th term is included)

• S=1/2*30(12+99)= 1665

The sum of all two - digit natural numbers which are divisible by 3 is 1665