10. Find the sum of first 20 even numbers,
Answers
Answered by
1
Answer:
2+4+6+8+10+12+14+16+18+20+22+24+26+28+30+32+34+36+38+40=420
is answer so it helps you
Answered by
1
Step-by-step explanation:
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]
⇒S =n[2+n−1]
⇒Sn =n(n+1) ...(1)
Put n=20 in (1), we get
S 20 =20(20+1)
=420
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