Question

1. What is the sum of the first 20 multiples of five?

OS20 = 1,050
OS20 = 1,000
OS20 = 1,550
OS20 = 2,100

Answer 1

I’m not sure if this what your looking for ur hopefully it is correct:)

Correct option is B)
The sum of first n terms of arithmetic series formula can be written as,
S
n
​
=
2
n
​
[2a+(n−1)d]
Where n = number of terms ⇒ 20
a = first odd number ⇒ 2
d = common difference of A.P. ⇒ 2
Apply the given data in the formula,
S
20
​
=
2
20
​
[2×2+(20−1)2]
=10[4+(19)2]
=10[4+38]
=10[42]
=420
So, the sum of first 20 multiples of 2 is 420.