JAMB - Mathematics (1993 - No. 35)
The mean of the ages of ten secondary school pupils is 16 but when the age of their teacher is added to it the men becomes 19. Find the age of the teacher
27
35
38
49
คำอธิบาย
Average age of 110 students = 16
∴ Total age = 16 x 10 = 160 years
Age of teachers = x, total number of people now = 11
mean age = 19
Total age of new group = 19 x 11 = 209
Age of teachers = x = (209 - 160) = 49 yrs
∴ Total age = 16 x 10 = 160 years
Age of teachers = x, total number of people now = 11
mean age = 19
Total age of new group = 19 x 11 = 209
Age of teachers = x = (209 - 160) = 49 yrs