please solve this question

Question

In the last 4 days, a police officer has issued an average of 9 parking tickets per day. How many tickets would he/she have to issue on the 5th day to average 8 parking tickets per day?

Answer 1

In the 4 days we have issued 4(9) = 36 tickets

 

We want the average after 5 days to equal 8.

Take the arithmetic average of 5 numbers.. the first 4 of which total to 36 ...

and set it equal to 8

 

(36 + x)/5 = 8

36 + x = 40

x = 40 - 36

x = 4

 

If he issues 4 tickets on day 5 he will average 8 tickets per day

 

check:  (36+4)/5 = 8

            40/5 = 8

            8 = 8