Question

find the sum of first 20 terms of an AP 3,8,13....​

Answer 1

Answer:

1010

Step-by-step explanation:

AP- 3,8,13

a- 3

d- 5

n- 20

Sum= n/2{2a+(n-1)d}

20/2{2(3)+(20-1)5}

10{6+(19)5}

10{6+95}

10{101}

Sum= 1010

Answer 2

The sum of first 20 terms is 1010

Given : The AP series is, 3,8,13.

To find : The sum of the first 20 terms.

Solution :

We can simply solve this mathematical problem by using the following mathematical process. (our goal is to calculate the sum of the first 20 terms)

Here, we will be using the general formulas of AP series.

Now,

• First term of AP (a) = 3
• Common difference (d) = Second term - First term = 8-3 = 5
• Number of terms (n) = 20

So,

Sum of n number of terms of an AP series = (n/2) × [2a+(n-1) × d]

By, putting the available data, we get :

Sum of first 20 terms = (20/2) × [(2×3)+(20-1)×5]

or,

Sum of first 20 terms = 10 × (6+95)

or,

Sum of first 20 terms = 10 × 101

or,

Sum of first 20 terms = 1010

(This will be considered as the final result.)

Hence, sum of the first 20 terms is 1010