# Averages ( 11 to 15 )

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Averages ( 11 to 15 ):

# APTITUDE QUESTIONS (AVERAGES):

11. The average age of 37 students in a group is 15 years when teacher’s age is included to it, the average increases by one. What is the teacher’s age in years?

A)    31

B)    36

C)    53

D)    24

E)    None of these

Explanation:

Age of teacher = (38 * 16 – 37 * 15) years = 53 years

12. The average age of the mother and her six children is 12 years which is reduced by 5 years if the age of the mother is excluded. How old is the mother?

A)    42 years

B)    32 years

C)    40 years

D)    50 years

E)    None of these

Explanation:

Age of the mother = (12 * 7 – 7 * 6) years = 42 years.

13. The average age of 8 women is increased by 2 years when two of them whose ages are 21 years and 23 years are replaced by two new women. What is the average age of the two new women is:

A)    25 years

B)    26 years

C)    29 years

D)    30 years

E)    None of these

Explanation:

The total age increased = (8 * 2) years = 16 years
Sum of ages of two new women = (21 + 23 + 16) = 60 years
∴ Average age of two new women = 60/2=30

14. A motorist travels to a place 150 km away at an average speed of 50 km/hr and returns at 30 km/hr. What will be his average speed for the whole journey in km/hr?

A)    35

B)    37

C)    37.5

D)    40

E)    None of these

Explanation:

Average speed = 2xy/(x+y) km/hr= [ (2*50*30)/(50+30) ] km/hr=37.5 km/hr

15. Three years ago, the average age of X and Y was 20 years. As Z joins them, the average age becomes 22 years. How old Z is now?

A)    20 years

B)    27 years

C)    28 years

D)    30 years

E)    None of these

Explanation:

Present age of (X + Y) = (20 * 2 + 3 * 2) = 46 years
Present age of (X + Y + Z) = (22 * 3) years = 66 years
∴ C’s age = (66 – 46) years = 20 years