What is the sum of the arithmetic series below?
15
e fn=4i-1
i=1
a. 930
b. 868
c. 434
d. 465

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.

The mode of the numbers is 29.