Question

What is the sum of the first 35 numbers in the arithmetic series
124 + 133 + 142 + 151 + ⋯?

A. 5,690
B. 9,566
C. 9,659
D. 9,695
E. 10,010

Answer 1

a=124 , d=9 (the difference) , n = 35

plug them in the formula:

S=n/2(2a + (n-1)d)

Answer 2

It is D

Answer 3

Check it for yourself

Answer 4

a1 = 124
d = 9
n = 35

an = a1 + (n - 1) * d
a35 = 124 + (35 - 1) * 9
a35 = 124 + 34 * 9
a35 = 124 + 306
a35 = 430 (this is just the 35 term)

sn = n(a1 + an) / 2
s35 = 35(124 + 430) / 2
s35 = 35 (554)/2
s35 = 19390/2
s35 = 9695

I agree....answer is D