Question

*What is the sum of first 20 natural numbers ?*

1️⃣ 190
2️⃣ 210
3️⃣ 200
4️⃣ 220​

Answer 1

Given,

The numbers are = First 20 natural numbers

To find,

The sum of the first 20 natural numbers.

Solution,

We can simply solve this mathematical problem by using the following mathematical process.

Here, we have to take help of the Arithmetic progression method.

First term of AP (a) = 1

Common difference (d) = 1

Number of terms (n) = 20

Sum of the terms = n/2 [2a+(n-1)d]

= 20/2 [2×1+(20-1)×1]

= 10 × (2×1+19×1)

= 10× (2+19)

= 210

Hence, the sum will be 210.

Answer 2

SOLUTION

TO CHOOSE THE CORRECT OPTION

What is the sum of first 20 natural numbers

1. 190

2. 210

3. 200

4. 220

FORMULA TO BE IMPLEMENTED

If in an arithmetic progression

Number of terms = n

First term = a and last term = l

Then sum of n terms

$\displaystyle \sf{ = \frac{n}{2} \bigg(a + l \bigg) }$

EVALUATION

We have to find sum of first 20 natural numbers

First 20 natural numbers are 1 , 2 ,..., 20

This is an arithmetic progression with

First term = a = 1

Last term = l = 20

Number of terms = n = 20

So the required sum

$\displaystyle \sf{ = \frac{n}{2} \bigg(a + l \bigg) }$

$\displaystyle \sf{ = \frac{20}{2} \bigg(1 + 20 \bigg) }$

$\displaystyle \sf{ = 10 \times 21}$

$\displaystyle \sf{ =210}$

FINAL ANSWER

The correct option is 2. 210

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