Answer:
[tex]9a+36[/tex]
Step-by-step explanation:
The average (arithmetic mean) of four numbers is 4a + 16. When a fifth number is added, the average becomes 5a + 20.
The average (arithmetic mean) of four numbers is 4a + 16.
Sum of 4 numbers = 4 times the average
Sum of 4 numbers =[tex]4(4a+16)= 16a+64[/tex]
sum of 5 numbers = 5 times the average of 5 numbers
Sum of 5 numbers =[tex]5(5a+20)=25a+100[/tex]
fifth number = sum of 5 numbers minus the sum of 4 numbers
[tex]fifth \ number = 25a+100-(16a+64)[/tex]
[tex]25a+100-16a-64[/tex]
[tex]9a+36[/tex]
