Q- Sum of 20 even numbers?
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Posted by Shivam Maheshwari 5 years ago
- 3 answers
Yogita Ingle 5 years ago
We have to find the sum n terms of the AP 2,4,6,...
Here a=2,d=4−2=2.
Therefore, Required sum Sn=n/2 [2a+(n−1)d]=n/2 [2×2+(n−1)×2]
⇒Sn=n[2+n−1]
⇒Sn=n(n+1) ...(1)
Put n=20 in (1), we get
S20=20(20+1)=420
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Sathi Gupta 5 years ago
0Thank You