FACTS  AND  FORMULAE  FOR  AVERAGE QUESTIONS

 

 

1. Average =Sum of observationsNo. of observations

2. Suppose a man covers a certain distance x kmph and an equal distance at y kmph. Then, the average speed during the whole journey is2xyx+yKmph

Q:

Navaneet has thrice the money Poonam has and Poonam has 25% more money than Hebah. If the average money of the three is Rs. 350, What is the amount that Navaneet has ?

A) Rs. 175 B) Rs. 220.75
C) Rs. 218.55 D) Rs. 656.25
 
Answer & Explanation Answer: D) Rs. 656.25

Explanation:

Assume Hebah has Rs. M

Since 25% more money at Poonam

=> Money at Poonam = M + (25% of M)

=> Money at Poonam = M + 0.25M = Rs. 1.25M

Money with Navaneet is thrice the money with Poonam,

=> Money at Navaneet = 3(1.25M) = Rs. 3.75M

Now, sum of all Money = (M + 1.25M + 3.75M) = Rs. 6M

But given the average of the money is Rs. 350

=> 6M/3 = 350

=> 2M = 350

=> M = 350/2 = Rs. 175

=> Amount of money Navaneet has = Rs. 3.75M = 3.75 x 175 = Rs. 656.25.

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Q:

Consider the following grouped frequency distribution:

  x           f

0-10       8

10-20     12

20-30     10

30-40      p

40-50      9

 

If the mean of the above data is 25.2, then what is the value of p?

 

A) 9 B) 10
C) 11 D) 12
 
Answer & Explanation Answer: C) 11

Explanation:
Mean = (sum of fixi/ (sum of f) = (8*5 + 12*15 + 10*25 + P*35 +9*45) / (8+12+10+P+9) = 25.2
(875 + 35P)/(39+P) = 25.2
P = 11
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Q:

The average score of boys in an examination in a school is 81 and that of the girls is 83 and the average score of the school is 81.8. Then what will be ratio between the number of girls to the number of boys, in the examination?

A) 3:2 B) 2:3
C) 4:3 D) 3:4
 
Answer & Explanation Answer: B) 2:3

Explanation:

Let the number of boys = b

Let the number of girls = g

From the given data,

 

81b + 83g = 81.8(b + g)

81.8b - 81b = 83g - 81.8g

0.8b = 1.2g

b/g = 1.2/0.8 = 12/8 = 3/2

=> g : b = 2 : 3

 

Hence, ratio between the number of girls to the number of boys = 2 : 3.

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Q:

Find the average of first 20 multiples of 9.

 

A) 94.8 B) 94.7
C) 94.6 D) 94.5
 
Answer & Explanation Answer: D) 94.5

Explanation:
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Q:

If the average of 31, x, 42, 39, 56, 78, 83 and 91 is 58.5, then what is the value of x?

 

A) 26 B) 34
C) 58 D) 48
 
Answer & Explanation Answer: D) 48

Explanation:
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Q:

Average of 10 numbers is 14. If each number is multiplied by 6, then what will be the new average?

 

A) 70 B) 84
C) 56 D) 92
 
Answer & Explanation Answer: B) 84

Explanation:
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Q:

The median of the data 1, 1/2, 1/2, 3/4, 1/4, 2, 1/2, 1/4, 3/4 is

 

A) 1/4 B) 1/2
C) 1/6 D) 3/4
 
Answer & Explanation Answer: B) 1/2

Explanation:
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Q:

The average marks of 50 students in an examination was 65. It was later found that the marks of one student had been wrongly entered as 83 instead of 38. The correct average is?

A) 63.9 B) 64.5
C) 64.7 D) 64.1
 
Answer & Explanation Answer: D) 64.1

Explanation:
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