Average (7)

1. Suresh drives his car to a place 150 km away at an average speed of 50 km/hr and returns at 30 km/hr. What is his average speed for the whole journey ?
1. 32.5 km/hr.
2. 35 km/hr.
3. 37.5 km/hr
4. 40 km/hr

Answer & Explanation

Answer:- 3

Explanation :-

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

 

2. 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. What is the average age of the family ?
1. 21 years
2. 20 years
3. 18 years
4. 19 years

Answer & Explanation

Answer:- 4

Explanation :-

Sum of the present ages of husband, wife and child = (23 * 2 + 5 * 2) + 1 = 57 years.
Average Age of family = (57/3) = 19 years.

 

3. In an examination, a student’s average marks were 63. If he had obtained 20 more marks for his Geography and 2 more marks for his history, his average would have been 65. How many subjects were there in the examination?
1. 12
2. 11
3. 13
4. 14

Answer & Explanation

Answer:- 2

Explanation :-

Lets assume  the number of exams be x.
Therefore,
63x + 20 + 2 = 65x
2x = 22
x = 11.

 

4. The average salary of all the workers in a workshop is Rs.8000. The average salary of 7 technicians is Rs.12000 and the average salary of the rest is Rs.6000. How many workers are there in the workshop ?
1. 21
2. 22
3. 23
4. 24

Answer & Explanation

Answer:- 1

Explanation :-

Let’s assume the total number of workers be x
Therefore,
8000 x  = (12000 * 7) + 6000 (x – 7)
2000x = 42000
x = 21.

 

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