Aptitude - Average

Exercise :: Average - General Questions

11. 

The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:

A. 17 kg
B. 20 kg
C. 26 kg
D. 31 kg

Answer: Option D

Explanation:

Let A, B, C represent their respective weights. Then, we have:

A + B + C = (45 x 3) = 135 .... (i)

A + B = (40 x 2) = 80 .... (ii)

B + C = (43 x 2) = 86 ....(iii)

Adding (ii) and (iii), we get: A + 2B + C = 166 .... (iv)

Subtracting (i) from (iv), we get : B = 31.

B's weight = 31 kg.


12. 

The average weight of 16 boys in a class is 50.25 kg and that of the remaining 8 boys is 45.15 kg. Find the average weights of all the boys in the class.

A. 47.55 kg
B. 48 kg
C. 48.55 kg
D. 49.25 kg

Answer: Option C

Explanation:

Required average
= 50.25 x 16 + 45.15 x 8
16 + 8
= 804 + 361.20
24
= 1165.20
24
= 48.55

13. 

A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is:

A. 250
B. 276
C. 280
D. 285

Answer: Option D

Explanation:

Since the month begins with a Sunday, to there will be five Sundays in the month.

Required average
= 510 x 5 + 240 x 25
30
= 8550
30
= 285


14. 

If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55, 60, then the average marks of all the students is:

A. 53.33
B. 54.68
C. 55
D. None of these

Answer: Option B

Explanation:

Required average
= 55 x 50 + 60 x 55 + 45 x 60
55 + 60 + 45
= 2750 + 3300 + 2700
160
= 8750
160
= 54.68

15. 

A pupil's marks were wrongly entered as 83 instead of 63. Due to that the average marks for the class got increased by half (1/2). The number of pupils in the class is:

A. 10
B. 20
C. 40
D. 73

Answer: Option C

Explanation:

Let there be x pupils in the class.

Total increase in marks = x x 1 = x
2 2

x = (83 - 63)    x = 20      x= 40.
2 2


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