Question

Your electric bill has been as follows for the past six months:

Answer 1

To find the monthly average (mean), add all the numbers up and divide the answer by the total number of numbers you added up.

July: $78.56

August: $30.21

September: $81.20

October: $79.08

November: $66.18

December: $100.75

Add all the bills up.

$78.56 +

$30.21 +

$81.20 +

$79.08 +

$66.18 +

$100.75 =

$435.98

Divide $435.98 by 6 (because you added up 6 numbers).

$435.98 ÷ 6 = $72.66

$\boxed {D)~72.66~is~your~answer.}$

Answer 2

You want to find the monthly average over the past 6 months.

July: $78.56

August: $30.21

September: $81.20

October: $79.08

November: $66.18

December: $100.75

Add all of these up

(July) $78.56

(August) $30.21

(September) $81.20

(October) $79.08

(November) $66.18

(December) + $100.75

----------------------------------------------

(Total cost) $435.88

There are 6 months you are calculating for, therefore divide the total (combined) cost of 6 months with the total number of months (in this case, 6)

$435.88 (total cost of 6 months) ÷ 6 (months)

The average cost per month of over the past 6 months is $72.66.