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:

Ravi had five subjects in his final examination. The maximum marks in each subject are 100. If his percentage in four subjects is 80, and he scores 65 marks in the fifth subject, determine his overall percentage for the five subjects.

A) 0.78 B) 0.79
C) 0.77 D) 0.76
 
Answer & Explanation Answer: C) 0.77

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Q:

72% of a number is 90. What is the number?

A) 120 B) 125
C) 130 D) 124
 
Answer & Explanation Answer: B) 125

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Q:

In a class consisting of boys and girls, there are 45 students. If three fifth of the students are boys, find the number of boys in the class.

A) 25 B) 26
C) 27 D) 28
 
Answer & Explanation Answer: C) 27

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3 905
Q:

A pen is sold at a discount of 36.36%. If the marked price of the pen is Rs 14300, then what is the selling price of the pen?

 

A) 8600 B) 9100
C) 10200 D) 11700
 
Answer & Explanation Answer: B) 9100

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2 901
Q:

Two successive discounts of 10% and 25% are given by Raman on a shirt. If the marked price of the shirt is Rs 600, then what is the value (in Rs) of discount?

 

A) 195   B) 185  
C) 155   D) 135
 
Answer & Explanation Answer: A) 195  

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Q:

The value of a machine depreciates at the rate of 20% per annum. If its present value is Rs 96000, then what was the value (in Rs) of the machine 2 years ago?

 

A) 138240   B) 134400  
C) 150000   D) 144000
 
Answer & Explanation Answer: C) 150000  

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3 898
Q:

 Out of two numbers, 65% of the smaller number is equal to 45% of the larger number. If the sum of the numbers is 2574, then what is the value of larger number? 

 

A) 1521   B) 1471  
C) 1641 D) 1419
 
Answer & Explanation Answer: A) 1521  

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Q:

If 2/3 of a pizza costs Rs.300, then 3/5 of a pizza will cost

A) Rs. 180 B) Rs. 250
C) Rs. 225 D) Rs. 270
 
Answer & Explanation Answer: D) Rs. 270

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