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:

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 4703
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 4685
Q:

If P is 140, which is 40% more than Q, then 3/25 of Q is

A) 9 B) 12
C) 18 D) 24
 
Answer & Explanation Answer: B) 12

Explanation:

From the given data,

P = 140

But it is given that,

40% of Q + Q = 140 = P

=> Q + [40Q/100] = 140

=> [100Q + 40Q]/100 = 140

=> 140Q = 140 x 100

=> Q = 100

Now,

 3/25 of Q 

= (3/25) x 100

= 3 x 4 

= 12 

 

Required 3/25 of Q  = 12.

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25 4684
Q:

Mohan spends 23% of an amount of money on an insurance policy, 33% on food, 19% on children’s education and 16% on recreation. He deposits the remaining amount of Rs. 504 in bank. How much amount does he spend on food and insurance policy together?

A) Rs. 2326 B) Rs. 5876
C) Rs. 1741 D) Rs. 3136
 
Answer & Explanation Answer: D) Rs. 3136

Explanation:

Let total amount = Rs. P

Total expenditure = (23 + 33 + 19 + 16)% of P = 91%ofP

Remaining money = (100 - 91)% of P = 9% of P

But given in the question that,

9% of P = 504

9p/100 = 504

=> P = 50400/9

=> P = Rs. 5600

 

Required money spent on Food & Insurance = 23 + 33 %

= 56% of 5600

= 56 x 5600/100 = 56 x 56 = Rs. 3136

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5 4658
Q:

The price of pulses has increased by 25%. The percentage of reduction that a family should effect in the use of pulses so as not to increase the expenditure on this account is ?

A) 16% B) 20%
C) 84% D) 72%
 
Answer & Explanation Answer: B) 20%

Explanation:

Reduction in consumption
= P100+P X 100%
= 25100+25 X 100%
= 20%

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4 4559
Q:

The tax on an article decreases by 10% and its consumption increases by 10%. Find the effect percent on its revenue?

Answer

-10+10-10*10100  % = -1%


 


\inline \therefore Decrease in revenue = 1%

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Subject: Percentage Exam Prep: Bank Exams

13 4471
Q:

Three strategies P, Q and R have been initiated for cost cutting in a company producing respectively 20%, 30% and 10% savings. Assuming that they operate independently, what is the net saving achieved ?

A) 49.6% B) 50.4%
C) 33.67% D) 66.66%
 
Answer & Explanation Answer: A) 49.6%

Explanation:

As these three strategies P, Q and R are independent so these will cut cost one after the other.
If initial cost is Rs 100, then
20% cost is cut after initializing strategy P, then cost will remain 80% = 80
further 30% cost is cut after strategy Q, then cost will remain 70% of 80 = 56
further 10% cost is cut after strategy R, then cost will remain 90% of 56 = 50.4

Thus final cost remains 50.4 % of the original cost. Hence net saving is 100 - 50.4 = 49.6 %.

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3 4422
Q:

If L exceeds K by 30%, then K is less than L by ?

A) 14 2/5 % B) 23 1/3 %
C) 20 % D) 16 %
 
Answer & Explanation Answer: B) 23 1/3 %

Explanation:

K = 100 L = 130
130------ 30
100------- ? => 23 1/13 %

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3 4415