Question

Find the sum first three triangular numbers.

Answer 1

Dear Student,
The terms of triangular series are called triangular number.
A triangular series is obtained by continuous summation of natural numbers.
So if first term is 0+1=1, then the following terms will be:
1+2=3
3+3=6
6+4=10
10+5=15

Here 1,2,3,4,5 are consecutive natural numbers.
Hence 1,3,6,10,15 are triangular numbers.

So, sum of first three triangular numers are = 1+3+6=10
Regards!