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:

5/9 of the part of the population in a village are females. If 30 % of the females are married. The percentage of unmarried males in the total males is ?

A) 62.5 % B) 125 %
C) 84.32 % D) 46.87 %
 
Answer & Explanation Answer: A) 62.5 %

Explanation:

Let total population = p
number of females = 5p/9
number of males =(p-5p/9) = 4p/9
married females = 30% of 5p/9 = 30x5p/100x9 = p/6
married males = p/6
unmarried males =(4p/9-p/6) = 5p/18
Percentage of unmarried males in the total males = {(5p/18)/4p/9}x100 = (5p/18)x(9/4p) = 125/2 % = 62.5%

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Q:

Read the data given and answer the following questions

 

In a class of 60 students:

 

42 like Maths,

32 like English,

12 like neither Maths nor English

 

How many students like both Maths and English?

A) 28 B) 26
C) 16 D) 12
 
Answer & Explanation Answer: B) 26

Explanation:
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1 14170
Q:

In a factory there are three types of Machines M1 , M2 and M3 which produces 25%, 35% and 40% of the total products respectively. M1, M2 and M3 produces 2% , 4% and 5% defective products, respectively. What is the percentage of non-defective products?

A) 89% B) 97.1%
C) 96.1% D) 86.1%
 
Answer & Explanation Answer: C) 96.1%

Explanation:

Non- defective products

 

25x0.98+35x0.96+40x0.95100 x 100 = 96.1

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22 14165
Q:

A Shopkeeper  charges sales tax of x% upto Rs.2,000 and above it he charges y%. A customer pays total tax of Rs 320, when he purchases the goods worth Rs. 6,000 and he pay's the total tax of Rs. 680 for the goods worth Rs. 12,000. The value of (x-y) is:

A) 0 B) -2
C) -4 D) 5
 
Answer & Explanation Answer: B) -2

Explanation:

          2000xX100 + 4000xY100 = 320

 

and     2000xX100 + 10000xY100 = 680

 

x = 4  and  y = 6

 

x-y = -2

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14 14100
Q:

A number, when 35 is subtracted from it, reduces to its 80 percent. What is four - fifth of that number  ?

A) 175 B) 140
C) 135 D) 95
 
Answer & Explanation Answer: B) 140

Explanation:

x - 35 = 80x/100 

=> x = 175 

=> 4x/5 = 4x175/5 = 140.

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18 14051
Q:

Lagaan is levied on the 60% of the cultivated land. The revenue department collected total Rs. 3,84,000 through the lagaan from the village of Sukhiya. Sukhiya, a very rich farmer , paid only Rs.480 as lagaan. The percentage of total land of Sukhiya over the total taxable land of the village is:

A) 0.15% B) 15%
C) 0.125% D) None of these
 
Answer & Explanation Answer: D) None of these

Explanation:

Total land of Sukhiya = 480x/0.6 = 800x

 

Cultivated land of village = 384000x

 

Required percentage = 800x384000x 100 = 0.20833

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16 13478
Q:

The percentage discount offered for "Buy 6 get 1 free is" ?

A) 85.78 % B) 58. 48 %
C) 19.25 % D) 14.285 %
 
Answer & Explanation Answer: D) 14.285 %

Explanation:

Total Items = 7
Discounted = 1
Percentage = 1/7 x 100
= 14.285%

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16 13351
Q:

40% of 265 + 35% of 180 = 50% of ?

A) 383 B) 338
C) 84.5 D) 253.5
 
Answer & Explanation Answer: B) 338

Explanation:

We know that 40% = 25

 

40% of 265 + 35% of 180 = 50% ?

 

25 x 265 + 35% of 180 = 50% ?

 

We know that (35% of 180 = 180% of 35) & 180% = 95

 

25 x 265 + 95 x 35 = 50% ?

 

106 + 63 = 50% ?

 

?= 2 x 169 = 338.

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