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:

If U = 450 and V = 585, then V is how much percentage more than U?

A) 130 B) 23.07
C) 25 D) 30
 
Answer & Explanation Answer: D) 30

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Q:

If 21% of an electricity bill is discounted, Rs 1817 is still to be paid. How much was the original bill amount?

A) Rs 1502 B) Rs 2336
C) Rs 2300 D) Rs 1538
 
Answer & Explanation Answer: C) Rs 2300

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Q:

20% discount is offered on an item. By applying a promo code the customer wins 15% cash back. What is the effective discount?

A) 30.8 percent B) 30 percent
C) 12 percent D) 32 percent
 
Answer & Explanation Answer: D) 32 percent

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Q:

If 35% of (x + y) = 40% of (x – y), then x is what percentage of y?

A) 1500 B) 150
C) 15 D) 105
 
Answer & Explanation Answer: A) 1500

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Q:

If the edge of a cube is increased by 10%, then what will be the percentage increase in its volume ?

A) 30 B) 31.3
C) 136.1 D) 33.1
 
Answer & Explanation Answer: D) 33.1

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Q:

If the successive discounts be 20% , 10% and 5% , then the single equivalent rate of discount is

A) 31.6% B) 31.5%
C) 31% D) 31.4%
 
Answer & Explanation Answer: A) 31.6%

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Q:

An engineering student has to secure 25% marks to pass. He gets 47 and fails by 43 marks. What are the maximum marks of the examination?

A) 385 marks B) 410 marks
C) 360 marks D) 435 marks
 
Answer & Explanation Answer: C) 360 marks

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Q:

If the shopkeeper sells an item at Rs 4400 which is marked as Rs 5000, then what is the discount that he is offering?

A) 20% B) 12%
C) 15% D) 10%
 
Answer & Explanation Answer: B) 12%

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