Zacs grade in math improved every semester by 50 on his prev

Zac\'s grade in math improved every semester by 50% on his previous semester grade, so that at the end of the fifth semester his grade was 81%. What was his average (mean) grade over the five semesters?                           

a. 31.4%

b. 38.0%

c.42.2%

d. 48.5%

Solution

Zac\'s grade in 4 the semester = x

x + 50% of x = 81%

1.5x = 81

x = 54

Zac\'s grade in 3 semester = y

1.5y = 54

y = 36

Zac\'s grade in 2nd semester= z

1.5z = 36

z = 24

Zacgrade in 1 semester= a

1.5a = 24

a = 16

Therefore, average grade over 5 semester

= ( 16 + 24 + 36 + 54 + 81)/5

= 42.2%