Question

find the sum of first 20 even natural number​

Answer 1

Answer:

Hence find the sum of first 20 even natural numbers. ∴ Sum of first twenty even natural numbers is 420.

Answer 2

Answer:

The sum of first 20 even natural numbers is 420

                                                                                                                             

Step-by-step explanation:

Sum of n terms of a AP = $\frac{n}{2} [2a + (n - 1)d]$

where,

• a is the first term of the A.P.
• n is the number of terms in the A.P.
• d is the common difference of the A.P.

Sum of first 20 natural numbers :-

• first term (a) = 2 (as even natural numbers start from 2)
• no. of terms (n) = 20
• common difference (d) = 2 (as  [4-2=2], [6-4=2])

Sum =  $\frac{n}{2} [2a + (n - 1)d]$

= $\frac{20}{2}$ [2 x 2 + (20 - 1) x 2]

=  10 x [4 + 38]

= 10 x 42

= 420