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:

 The difference between a number and its two-fifth is 510. What is 10% of that number ?

A) 75 B) 85
C) 95 D) 105
 
Answer & Explanation Answer: B) 85

Explanation:

Let the number be x. Then, x-(2/5)x = 510

=> 3x/5 =510 

=>x =[510 * ( 5/3)] =850 

10 % 0f 850 = 85.

Report Error

View Answer Report Error Discuss

Filed Under: Percentage

40 21621
Q:

What percent of a day is 3 hours?

A) 14.9% B) 12.5%
C) 15.6%% D) 11.4%
 
Answer & Explanation Answer: B) 12.5%

Explanation:

Let p% of a day is 3 hrs.

We know that a day has 24 hrs.

=> p x 24/100 = 3

=> p = 300/24

=> p = 12.5%

 

Hence, 3 hrs is 12.5% of a day.

Report Error

View Answer Report Error Discuss

24 21527
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 percentage of students who passed in all subjects?

A) 8 B) 12
C) 7 D) 10
 
Answer & Explanation Answer: C) 7

Explanation:
Report Error

View Answer Report Error Discuss

Filed Under: Percentage
Exam Prep: Bank Exams

4 21472
Q:

A district has 64000 inhabitants. If the population increases at the rate of 2 * 1/2 % per annum, then the number of inhabitants at the end of 3 years will be : 

A) 65380 B) 68921
C) 70987 D) 72345
 
Answer & Explanation Answer: B) 68921

Explanation:

Population afer 3 years = 64000 * (1 +  5/(2 *100) )^3 = (64000 * 41/40 * 41/40 * 41/40 ) = 68921..

Report Error

View Answer Report Error Discuss

Filed Under: Percentage

57 21230
Q:

A number is increased by 20% and then decreased by 20%, the final value of the number is ?

A) increase by 2% B) decrease by 3%
C) decrease by 4% D) increase by 5%
 
Answer & Explanation Answer: C) decrease by 4%

Explanation:

Here, x = 20 and y = - 20
Therefore, the net % change in value
=x + y + xy100 %
20 + -20 + 20 × -20100%  or  - 4%

Since the sign is negative, there is a decrease in value by 4%.

Report Error

View Answer Report Error Discuss

Filed Under: Percentage
Exam Prep: GRE , GATE , CAT , Bank Exams , AIEEE
Job Role: Bank PO , Bank Clerk , Analyst

34 21085
Q:

An agent, gets a commission of 2.5% on the sales of cloth. If on a certain day, he gets Rs. 12.50 as commission, the cloth sold through him on that day is worth

A) 300 B) 500
C) 700 D) 900
 
Answer & Explanation Answer: B) 500

Explanation:

Let the total sale be Rs. x.

 

Then, 2.5%. of x = 12.50

=> (25/100 * 1/100 * x) =  125/10

=> x = 500.

Report Error

View Answer Report Error Discuss

Filed Under: Percentage

30 20929
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:
Report Error

View Answer Report Error Discuss

Filed Under: Percentage
Exam Prep: Bank Exams

2 20776
Q:

The ratio of earnings of A and B is 4:5. If the earnings of A increase by 20% and the earnings of B decrease by 20%, the new ratio of their earnings becomes 6:5. What are A's earnings?

A) Rs.22,000 B) Rs.27,500
C) Rs. 26,400 D) Cannot be determined
 
Answer & Explanation Answer: D) Cannot be determined

Explanation:
Report Error

View Answer Report Error Discuss

Filed Under: Percentage
Exam Prep: Bank Exams
Job Role: Bank PO

100 20460