Question

Find the sum of the first 20 odd natural numders

Answer 1

Answer: 100.

Sum of first 20 odd natural numbers is 100.

Step-by-step explanation:

First 20 natural odd numbers are 1,3,5,7,9,11,13,15,17,19.

Now sum of first 20 odd natural numbers are: 1+3+5+7+9+11+13+15+17+19.

= 100.

Hope it's easy and very helpful.

Answer 2

Question:-

Find the sum of the first 20 odd natural numbers

Solution:-

First 20 odd natural number are

1 , 3 , 5 , 7 , 9 , ................

So,

First terms ( a ) = 1 , Common difference ( d ) = 3 - 1 = 2

n = 20

$\color{olive} \bf \: S _n = \frac{n}{2} \{2a \: + (n - 1)d \}$

Put the number

$\bf \: \large \: S \small \: 20 \large \: = \frac{20}{2} \{2 \times 1 + (20 - 1) \times 2 \}$

$= \bf \: 10 \{2 + (19) \times 2 \}$

$\bf \: = 10 \{2 + 38 \}$

$\bf \: = 10 \{40 \}$

$\bf \: = 400$

Sum of 20 odd natural number is 400