ExamAdept

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: C

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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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: B

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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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: D

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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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: C

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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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: D

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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Questions for: Average