Question

Solve:
(1)+(1+2)+(1+2+3)+..........................+(1+2+3+4+.............+15)

Answer 1

Step-by-step explanation:

we can Solve:

(1)+(1+2)+(1+2+3)+..........................+(1+2+3+4+.............+15) by using sum of first n natural numbers

n(n+1)/2

1+3+6+10+15+21+28+36+45+55+66+78+91+105+

120

these numbers are triangular numbers

sum of first n triangular numbers are n(n+1)(n+2)/6

15(15+1)(15+2)/6

5×8×17

=680

Answer 2

Answer:

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