find the sum of all natural numbers from 1 to 20
Answers
Answered by
1
Answer:
may be.......
210....
hope it helped....
Answered by
2
Answer:
We have to find the sum n terms of the AP 1,2,3,...
Here
a=1,d=1.
Therefore, Required sum S
n
=
2
n
[2a+(n−1)d]=
2
n
[2×1+(n−1)×1]
⇒S
n
=
2
n
[2+n−1]
⇒S
n
=
2
n(n+1)
...(1)
Put n=20 in (1), we get
S
20
=
2
20(20+1)
=210
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