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:

What should come in place of question mark (?) in the following question?

45% of 400+ √? = 56% of 750 - 40% of 350

A) 10000 B) 1000
C) 10201 D) 9801
 
Answer & Explanation Answer: A) 10000

Explanation:

45/100×400+√?=56/100 ×750 -40/100 ×350

180 + √? = 420 - 140 180 + √? = 280 √? = 280 - 180 √? = 100 ? = 1002 ? = 10000

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1 52949
Q:

A number is decreased by 10% and then increased by 10%.  The number so obtained is 10 less than the original number. What was the oiginal number ? 

A) 1000 B) 2000
C) 3000 D) 4000
 
Answer & Explanation Answer: A) 1000

Explanation:

Let the original number be x.

 

Final number obtained = 110% of (90% of x) =(110/100 * 90/100 * x) = (99/100)x. 

 

x-(99/100)x=10

=> x =1000

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141 50858
Q:

If A's height is 40% less than that of B, how much percent B's height is more than that of A?

A) 66.66% B) 76.66%
C) 96.66% D) 86.66%
 
Answer & Explanation Answer: A) 66.66%

Explanation:

Excess of B's height over A's = [(40/(100 - 40)] x 100% =  66.66%

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198 50475
Q:

What is the value of 88% of 1125 + 20% of 425?

 

A) 1025 B) 1125.2
C) 1075 D) 1055
 
Answer & Explanation Answer: C) 1075

Explanation:
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Q:

A housewife saved Rs. 2.50 in buying an item on sale. If she spent Rs. 25 for the item, approximately how much percent she saved in the transaction ?

A) 8 B) 9
C) 10 D) 11
 
Answer & Explanation Answer: B) 9

Explanation:

Actual price = Rs. (25 + 2.50) = Rs. 27.50. 

 

Saving = 2.50

 

Percentage Saving = [(2.50/27.50)*100]

 

= 2500/275

 

9111%

 

9%

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111 47640
Q:

A shopkeeper offers the following 3 schemes. Which scheme has the maximum discount percentage?

I. Two successive discount of 20% and 25%

II. Buy 5 get 3 free

III. Buy 5 get 6

 

A) Only II B) Only I
C) Only I and II D) Only I and III
 
Answer & Explanation Answer: B) Only I

Explanation:
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Q:

If 60% of a number is added to 60, then the result is equal to the number itself. What is the number?

 

A) 150   B) 120  
C) 100   D) 180  
 
Answer & Explanation Answer: A) 150  

Explanation:
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Q:

Read the data given below and answer the questions based on it.

 

In the CBSE Board exams last year, 53% passed in Biology, 61% percent passed in English, 60% in Social studies, 24% in Biology and English, 35% in English and social studies, 27% in Biology and social studies and 5% in none.

 

What is the ratio of percentage of students who passed in Biology and Social Studies but not English in relation to the percentage of students who passed in Social Studies and English but not Biology?

A) 5:7 B) 7:5
C) 4:5 D) 5:4
 
Answer & Explanation Answer: A) 5:7

Explanation:
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