Question

What is the sum of the arithmetic series below?

Answer 1

Our question transforms to finding the following sum : 3 + 7 + 11 + 15.... upto 15 terms 

Use formula for sum of an AP series 

S = (n * (2a + (n - 1)d)) / 2 

n -> no of terms in AP series , so n = 15 
a -> first term in series, so a = 3 
d -> common difference, so d = 4 

Put all values for a, n, d and you will get the sum.