EXERCISE 6.A (OBJECTIVE TYPE QUESTIONS) (IN 71 75 SOLUTION)

71.       A motorist travels to a place 150 km away at an average speed of 50 km / hr and returns at 30 km / hr. His average speed for the whole journey in km /hr is:

a)      35

b)      37

c)       37.5

d)      40

72.       The average weight of 3 men A, B and C is 84 kg. Another man D joins the group and the average now becomes s 80 kg. If another man E, whose weight is 3 kg more than that of D, replaces a, then the average weight of B, C, D and E becomes 79 kg. The weight of A is.

a)      70 kg

b)      72 kg

c)       75 kg

d)      80 kg

73.       The average age of a husband and his wife was 23 years at the time of their marriage. After five years they have a one-year old child. The average age of the family now is:

a)      19 years

b)      23 years

c)       28.5 years

d)      29.3 years

74.       There years ago, the average age of A and B was 18 years. With C joining them, the average age becomes 22 years. How old is C now?

a)      24 years

b)      27 years

c)       28 years

d)      30 years

75.       The average age of husband, wife and their child 3 years ago was 27 years and that of wife and the child 5 years ago was 20 years. The present age of the husband is:

a)      35 years.

b)      40 years

c)       50 years

d)      None of these

ANSWERS

71.C

72.C

73.A

74.A

75.B

SOLUTION 

71.       Average speed = 2xy / X + y km / hr = (2 x 50 x 30 / 50 + 30 ) km / 

hr = 37. 5 km /hr.

72.       Let A, B, C, D and E represent their respective weights. Then,

A + B + C = (84 x 3) = 252 kg, A + B + C + D = (80 x 4 ) =320 kg.

D = (320 – 252) kg = 68 kg, E = (68 + 3) kg = 71kg.

B + C + D + E = (79 x 4 = 316 kg.

Now, (A + B + C + D) – (B + C + D + E)  = (320 – 316) kg = 4 kg.

A – E = 4   A = (4 + E ) = 75 kg.

73.       Sum of the present ages of husband, wife and child = (23 x 2 + 5 x 2) + 1= 57 years.

Required average = (57 / 3 ) = 19 years.

74.       Present age of (A + B = (18 x 2 + 3 x 2) years = 42 years.

Present age of (A + B + C ) = (22 x 3 years = 66 years.

C’s age = (66 -42) years = 24 years.

75.       Sum of the present ages of husband, wife and child = (27 x 3 + 3 x 3 x 3) years = 90 years.

Sum of the present ages of wife and child = (20 x 2 +5 x 2) years = 50 years 

Husband’s present age = (90 – 50) years = 85 years.