Question

find the sun of the first 20 terms of ap 3,7,11,15 using formula
​

Answer 1

HeYa❤️...

Answer:

Given:

First term (a) = 3

Common difference (d) = 7-3 = 4

number of terms (n) = 20

______________________

Solution:

$sn = \frac{n}{2} \times 2a + (n - 1)d \\ \\ = \frac{20}{2} \times 2(3) + (20 - 1) \times 4 \\ \\ = 10 \times 6 + 76 \\ \\ = 60 + 76 \\ \\ = 136$

I hOpe It HeLpS Ya!

✌️✌️✌️✌️

Answer 2

Answer:

The sum of the first 20 terms is 820.

Step-by-step explanation:

a(first term) = 3

d(common difference)=4

n( number of terms) = 20

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

$Sum_{20} = \frac{20}{2} *(2*3+(20-1)4)$

     $=10(6+(19*4))$

       $= 10(6+76)$

      $= 10*82$

     = 820

If this answer is helpful, please mark it the brainliest:)