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 Percentage Questions

Popular Latest Rated Important Formulae

FACTS  AND  FORMULAE  FOR  PERCENTAGE  QUESTIONS

 

 

I.Concept of Percentage : By a certain percent , we mean that many hundredths. Thus x percent means x hundredths, written as x%.

To express x% as a fraction : We have , x% = x/100.

Thus, 20% = 20/100 = 1/5;     

48% = 48/100 = 12/25, etc.

To express a/b as a percent : We have, ab=ab×100% .

 

Thus, 14=14×100%=25%

   

 

II. If the price of a commodity increases by R%, then the reduction in consumption so as not to increase the expenditure is R100+R×100%

If the price of the commodity decreases by R%,then the increase in consumption so as to decrease the expenditure is R100-R×100%

 

 

III. Results on Population : Let the population of the town be P now and suppose it increases at the rate of R% per annum, then :

1. Population after n years = P1+R100n

 

2. Population n years ago =  P1+R100n

 

 

IV. Results on Depreciation : Let the present value of a machine be P. Suppose it depreciates at the rate R% per annum. Then,

1. Value of the machine after n years = P1-R100n

 

2. Value of the machine n years ago = P1-R100n

 

 

V. If A is R% more than B, then B is less than A by

R100+R×100%    

If A is R% less than B , then B is more than A by 

R100-R×100%  

Q:

In a competitive examination, the average marks for the entire examination was 60 marks. If 20% of the applicants scored 85 marks and 25% scored 95 marks. What was the average marks of the remaining applicants in the examination ?

A) 60 B) 52
C) 45 D) 35
 
Answer & Explanation Answer: D) 35

Explanation:

Let the total applicants be 100

 

Then, 20% got 85 marks

i.e 20 x 85 = 1700

 

and 25% got 95 marks

 i.e 25 x 95 = 2375

 

Now, the remaining applicants are 55 and let the average marks scored by them be x.

 

Therefore, 2375 + 1700 + 55x  =  60×100 

6000 - 4075 = 55x

55x=1925

x=35.

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8 4812
Q:

Population of a colony of mosquitoes is increasing by 20% per day. If the population on Monday was 3000, on which day of that week the population would be 5184 ?

A) Thursday B) Friday
C) Tuesday D) Monday
 
Answer & Explanation Answer: A) Thursday

Explanation:

Given monday population = 3000
Per day 20% increase in population.

Tuesday population = 3000 + 3000x20/100 = 3000 + 600 = 3600

Wednesday population =3600 + 3600x20/100 = 3600 + 720 = 4320

Thursday population = 4320 + 4320x20/100 = 4320 + 864 = 5184

So that day is Thursday.

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3 4798
Q:

Value of vehicle at end of each year depreciates at the rate of 3/5th of value at the beginning. If Initial value is 10,000Rs then at the end of three years its value is ? 

A) Rs. 6000 B) Rs. 3600
C) Rs. 2160 D) Rs. 415
 
Answer & Explanation Answer: C) Rs. 2160

Explanation:

End of first year     :  10000 x (3/5) = Rs. 6000
End of second year :  6000 x (3/5) = Rs. 3600
End of third year    :  3600 x (3/5) = Rs. 2160

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2 4788
Q:

Madhu got 32% of the maximum marks in a Bank examination and failed by 8 marks. However, Kumar who took the same examination got 42% of the total marks and got 16 marks more than the cut-off marks. What was the cut-off marks in the examination ?

A) 76.8 B) 86.8
C) 78.8 D) 84.8
 
Answer & Explanation Answer: D) 84.8

Explanation:

Let 'M' be the maximum marks in the examination.

Therefore, Madhu got 32% of M = 32M/100 = 0.32M
And Kumar got 42% of M = 42M/100 = 0.42M.
In terms of the maximum marks Kumar got 0.42M - 0.32M = 0.1M more than Madhu. ---- (1)

The problem however, states that Kumar got 16 marks more than the cut-off mark and Madhu got 8 marks less than the cut-off mark. Therefore, Kumar has got 16 + 8 = 24 marks more than Madhu. ---- (2)

Now, Equating (1) and (2), we get
0.1M = 24 => M = 24/0.1 = 240
'M' is the maximum mark and is equal to 240 marks.
We know that Madhu got 32% of the maximum marks.
Therefore, Madhu got 32 x 240/100 = 76.8 marks.
We also know that Madhu got 8 marks less than the cut-off marks.

Therefore, the cut-off marks will be 8 marks more than what Madhu got
= 76.8 + 8 = 84.8.

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11 4752
Q:

60 percent of 2/7 of three-fourth of a number is 2664. What is the number ?

A) 20720 B) 21352
C) 25421 D) 24150
 
Answer & Explanation Answer: A) 20720

Explanation:

Let N be the required number. 

=> 60100x27x34xN=2664  

=> N = 2664x2x7x5/9  

=> N = 20720.

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10 4668
Q:

40% of 80?

A) 36 B) 32
C) 42 D) 44
 
Answer & Explanation Answer: B) 32

Explanation:

Here 40% of 80 is given as

40100 x 80 = 8 x 4 = 32

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7 4583
Q:

A man reads 3/7 of a book on a day and 2/5 of the remaining, on the second day. If the number of pages still unread are 36, how many pages did the book contain ?

A) 105 B) 101
C) 98 D) 109
 
Answer & Explanation Answer: A) 105

Explanation:

Let number of pages in a book = p

According to questions

p - [3p/7 + (2/5 x 4p/7)] = 36

= p - 23p/35 = 36

=> 12p = 36 × 35

p = 105

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10 4560
Q:

 83% of 2350 = ?

A) 1889.95 B) 1912.35
C) 1875.25 D) 1950.50
 
Answer & Explanation Answer: D) 1950.50

Explanation:
83% of 2350 = ?
 
83/100 x 2350
 
=8.3 x 235
 
=1950.50
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12 4529