Question:

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.

Options:
A.47.55 kg
B.48 kg
C.48.55 kg
D.49.25 kg
Answer: Option C

Required average = \(\left(\frac{50.25\times16+45.15\times8}{16+8}\right)\) 

\(=\left(\frac{804+361.20}{24}\right)\)

\(=\frac{1165.20}{24}\)

= 48.55

 

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More Questions Related to Quantitative Aptitude > Average :

Question 1.

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:

Options:
  1.    17 kg
  2.    20 kg
  3.    26 kg
  4.    31 kg
Answer: Option 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.

Threrfore B's weight = 31 kg.

Question 2.

In Aruns opinion, his weight is greater than 65 kg but less than 72 kg. His brother doest not agree with Arun and he thinks that Aruns weight is greater than 60 kg but less than 70 kg. His mothers view is that his weight cannot be greater than 68 kg. If all are them are correct in their estimation, what is the average of different probable weights of Arun?

Options:
  1.    67 kg.
  2.    68 kg.
  3.    69 kg.
  4.    Data inadequate
  5.    None of these
Answer: Option A

Let Arun's weight by X kg.

According to Arun, 65 < X < 72

According to Arun's brother, 60 < X < 70.

According to Arun's mother, X <= 68

The values satisfying all the above conditions are 66, 67 and 68.

Therefore Required average = \(\left(\frac{66+67+68}{3}\right)=\left(\frac{201}{3}\right)=67kg.\)

Question 3.

A car owner buys petrol at Rs.7.50, Rs. 8 and Rs. 8.50 per litre for three successive years. What approximately is the average cost per litre of petrol if he spends Rs. 4000 each year?

Options:
  1.    Rs. 7.98
  2.    Rs. 8
  3.    Rs. 8.50
  4.    Rs. 9
Answer: Option A

Total quantity of petrol 
consumed in 3 years = \(\left(\frac{4000}{7.50}+\frac{4000}{8}+\frac{4000}{8.50}\right)liters\)

\(=4000\left(\frac{2}{15}+\frac{1}{8}+\frac{2}{17}\right)liters\)

\(=\left(\frac{76700}{51}\right)liters\)

Total amount spent = Rs. (3 x 4000) = Rs. 12000.

Therefore Average Cost = Rs.\(\left(\frac{1700\times51}{76700}\right)=Rs.\frac{6120}{767}=Rs.7.98\)

Question 4.

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:

Options:
  1.    250
  2.    276
  3.    280
  4.    285
Answer: Option D

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

Required avarage = \(\left(\frac{510\times5+240\times25}{30}\right)\)

= \(\frac{8550}{30}\)

= 285

Question 5.

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:

Options:
  1.    53.33
  2.    54.68
  3.    55
  4.    None of these
Answer: Option B

Required average = \(\left(\frac{55\times50+60\times55+45\times60}{55+60+45}\right) \)

= \(\left(\frac{2750+3300+2700}{160}\right)\)

= \(\frac{8750}{160}\)

= 54.68

Question 6.

A pupils 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:

Options:
  1.    10
  2.    20
  3.    40
  4.    73
Answer: Option C

Let there be x pupils in the class.

Total increase in marks = \(\left(x\times\frac{1}{2}\right)= \frac{1}{2}\)

Therefore  \(\frac{x}{2}= \left(83-63\right) \Rightarrow \frac{x}{2}= 20 \Rightarrow x = 40.\)