Question

The sum of first 20 even natural numbers is *​

Answer 1

Answer:

78

Step-by-step explanation:

First 20 even natural numbers are:

2,4,6,8,10,.....

a = 2 ; d = 2 ; n =20

We know that, Sum of n terms =

$\huge \boxed{ = \frac{n}{2} \times 2a + (n - 1)d}$

So,

$\large \: s20 = \frac{20}{2} \times 2(2) + 19(2)$

= 10 × 4 + 38

= 40 + 38

= 78

Therefore, The sum of first 20 even natural numbers is 78...

hope it helps.

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Answer 2

The number series 2, 4, 6, 8, 10, 12, . . . . , 40. Therefore, 420 is the sum of first 20 even numbers.

a= 2

d = 2

n= 20

an= a + (n-1) d

an = 2 + ( 20 -1) 2

= 2+(19)x 2

= 2 + 38

= 40

S = n/2 (a + an)

S = 20/2 ( 2 + 40)

S= 10 x 42

S = 420