Question

Find the sum of first 20 terms
of arithmetic series 5 + 10+15

using Suitable formula​

Answer 1

Answer:

we know that a=5 and d=5 and s20=?

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

s20=20/2{2×5+(20-1) 5}

s20=10{10+(19) 5}

s20=10{10+95}

s20=10(105)

s20=1050

Answer 2

Concept:

Sum of AP:

S = n / 2 [ 2 a + (n − 1) × d]

Given:

We are given the arithmetic series:

5 + 10 + 15 ...

Find:

We need to find the sum of its first 20 terms.

Solution:

The formula is:

S = n / 2 [ 2 a + (n − 1) × d]

n = 20

a = 5

d = 5

Putting it in the formula, we get that:

S = 20 / 2 [ 2(5) + (20 - 1) × 5]

S = 10 [ 10 +19 × 5]

S = 10 [ 10 + 95]

S = 10 [ 105]

S = 1050

Therefore, we get the sum of the first 20 terms as 1050.

#SPJ2