Question

10. Find the sum of first 20 even numbers,​

Answer 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

Answer 2

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