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:

Sripad has scored average of 65 marks in three objects. In no subjects has he secured less than 58 marks. He has secured more marks in Maths than other two subjects. What could be his maximum score in Maths ?

A) 79 B) 77
C) 76 D) 73
 
Answer & Explanation Answer: A) 79

Explanation:

Assuming Sripad has scored the least marks in subject other than science,
Then the marks he could secure in other two are 58 each.
Since the average mark of all the 3 subject is 65.
i.e (58+58+x)/3 = 65
116 + x = 195
x = 79 marks.

Therefore, the maximum marks he can score in maths is 79.

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Q:

P, Q, R, S, T and U are six consecutive odd numbers and their average is 52. What is the product of P and U ?

A) 2212 B) 2154
C) 2349 D) 2679
 
Answer & Explanation Answer: D) 2679

Explanation:

Let x, x+2, x+4, x+6, x+8 and x+10 are six consecutive odd numbers.

Given that their average is 52

Then, x + x+2 + x+4 + x+6 + x+8 + x+10 = 52×6

6x + 30 = 312

x = 47

So Product = 47 × 57 = 2679

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Q:

The average monthly salary of 24 employees in an organisation is Rs. 1500. If the manager's salary is added, then the average salary increases by Rs. 400. What is the manager's monthly salary ?

A) Rs. 8840 B) Rs. 11,500
C) Rs. 12,800 D) Rs. 9450
 
Answer & Explanation Answer: B) Rs. 11,500

Explanation:

Manager's monthly salary

= Rs. (1900 x 25 - 1500 x 24) = Rs. 11,500

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Q:

A batsman scores 26 runs and increases his average from 14 to 15. Find the runs to be made if he wants top increasing the average to 19 in the same match ?

A) 74 B) 79
C) 72 D) 60
 
Answer & Explanation Answer: A) 74

Explanation:

Number of runs scored more to increse the ratio by 1 is 26 - 14 = 12
To raise the average by one (from 14 to 15), he scored 12 more than the existing average.
Therefore, to raise the average by five (from 14 to 19), he should score 12 x 5 = 60 more than the existing average. Thus he should score 14 + 60 = 74.

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Q:

In a mens hostel, there were 95 students. To accommodate 30 more students the average is decreased by rupees 5. But total expenditure increased by Rs.500. Find the total expenditure of the hostel now ?

A) Rs. 4680 B) Rs. 4420
C) Rs. 4960 D) Rs. 5480
 
Answer & Explanation Answer: A) Rs. 4680

Explanation:

Let the expenditure on the 95 students be 'x'

Then,

95x + 500 = 120(x – 5)
95x + 500 = 120x - 600
120x - 95x = 1100
25x = 1100
=> x = 44

Therefore, total expenditure of the hostel becomes
95 x 44 + 500 = 4680.

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Q:

20 men went to a restaurant. Ninteen of them paid Rs.70 each and the twentieth man paid Rs.90.25 more than the average of all the 20 men. What is the total bill ?

A) Rs. 1495 B) Rs. 548
C) Rs. 850 D) Rs. 1750
 
Answer & Explanation Answer: A) Rs. 1495

Explanation:

Let the average bill paid by twenty members = 'x'

But 19 men paid each = Rs. 70

20th man paid Rs. 90.25 more than the avg bill of 20 = x + 90.25

20x = 19(70) + x + 90.25
19x = 1330 + 90.25
19x = 1420.25
x = 1420.25/19 = Rs. 74.75

But the total bill = 20 x 74.75 = Rs. 1495.

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Q:

It costs Rs. p each to send the first thousand messsages and Rs. q to send each subsequent one . If r is greater than 1,000, how many Rupees will it cost to send r messages ?

A) 1000 (r - p) + pq B) 1000 p + qr
C) 1000 (r - q) + pr D) 1000(p - q) + qr
 
Answer & Explanation Answer: D) 1000(p - q) + qr

Explanation:

We need to find the total cost to send r messsages, r > 1000.

The first 1000 messsages will cost Rs.p each (Or) 

The total cost of first 1000 messsages = Rs.1000p

The remaining (r - 1000) messsages will cost Rs.q each (Or)

The cost of the (r - 1000) = Rs.(r - 1000)y

 

Therefore, total cost = 1000p + rq - 1000q

= 1000(p - q) + qr

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Q:

The average age of 7 boys is increased by 1 year when one of tem whose age is replaced by a girl. What is the age of the girl ?

A) 33 yrs B) 27 yrs
C) 21 yrs D) 29 yrs
 
Answer & Explanation Answer: D) 29 yrs

Explanation:

Let the avg age of 7 boys be 'p' years
Let the age of the girl be 'q' years
From given data,
The age of 7 boys = 7p years
Now the new average = (p + 1) when 22 yrs is replaced by q
Now the age of all 7 will become = 7(p + 1) yrs
Hence, 7p - 22 + q = 7(p + 1) yrs
7p - 22 + q = 7p + 7
q = 22 + 7 = 29

Therefore, the age of girl = q = 29 years.

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