average aptitude 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 & Explanation

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.

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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 & Explanation

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
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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 & Explanation

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

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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 & Explanation

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
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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 & Explanation

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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