Question

If the nth term of an AP is 5 + 2n , then the sum of its first 20 terms is
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Answer 1

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FORMULA TO BE IMPLEMENTED

Sum of first n terms of an arithmetic progression

$= \displaystyle \: \frac{n}{2} [2a + (n - 1)d ]$

Where First term = a

Common Difference = d

CALCULATION

The nth term of an AP = 5 + 2n

First term = a = 5+2 = 7

Second Term = 5+4 = 9

Common Difference = d = 9 - 7 =2

Hence the sum of its first 20 terms is

$= \displaystyle \: \frac{20}{2} [2 \times 7 + (20 - 1) \times 2 ]$

$= 10 \times (14 + 38) = 520$

Answer 2

Answer:

The correct answer of this question is $520$

Step-by-step explanation:

Given - The nth term of an AP is 5 + 2n

To Find - Write the  sum of its first 20 terms .

An arithmetic progression (AP) is a list or sequence of integers in which each phrase is obtained by adding a specified number to the previous term.

According to the question,

The nth term of an AP = $5 + 2n$

So, first term is the  $a = 5+2 = 7$

and second term is $5+4 = 9$

the common Difference = $d = 9 - 7 =2$

Hence, the sum of the first 20 terms is

$\frac{n}{2} ( 2a + ( n - 1 ) d )$

$\frac{20}{2} ( 2$ × $7 + ( 20 - 1 )$ × $2 )$

$10$ × $( 14 + 38 ) = 520$

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