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 Percentage Questions

Popular Latest Rated Important Formulae

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 average of a set of whole numbers is 27.2. when the 20% of the elements are eliminated from the set of numbers then the average become 34. The number of elements in the new set of numbers can be :

A) 27 B) 35
C) 52 D) 63
 
Answer & Explanation Answer: C) 52

Explanation:

only (c) is correct since it is divisible by 4.

 

Let the original number of element  be x then the new no.of elements will be 

 

            4x5 = K                               

 

So K must be divisible by 4

 

Since,      x =  Kx5/4

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11 11184
Q:

600 students took the test on physics and chemistry. 35% students failed in physics and 45% students failed in chemistry and 40% of those who passed in chemistry also passed in physics, then how many students failed in both:

A) 162 B) 138
C) 60 D) None of these
 
Answer & Explanation Answer: D) None of these

Explanation:

                  Physics             Chemistry

Failed           35%                    45%

Passed         65%                    55%

Passed in both = 22% of total student

percentage of students who are passed in any of the physics or chemistry or both =(65+55) - 22 = 98%

So, the percentage of students who are failed in both = 2%

Therefore, total failed (in both subjects) students = 12 

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14 11054
Q:

A number increased by 30% gives 390. The number is

A) 180 B) 300
C) 480 D) 260
 
Answer & Explanation Answer: B) 300

Explanation:

Let the number be 'N'
Given N + 30N/100 = 390
=> 130N/100 = 390
=> N = 390 x 10/13
=> N = 300.

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15 11052
Q:

At an examination in which maximum marks are 500. P got 10% less than Q, Q got 25% more than R and R got 20% less than S. If P got 360 marks what percentage of marks was obtained by S ?

A) 77 B) 74
C) 80 D) 83
 
Answer & Explanation Answer: C) 80

Explanation:

Let marks obtained by S = M

R's marks = 0.80M

Q's marks = 1.25 (0.80M)

P's marks = (0.90) (1.25) (0.80M)

= 0.9M

But 0.9M = 360

M = ?

M = 400

Hence % of marks obtained by S

= 400/500 x 100 = 80%.

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11 10733
Q:

The Shopkeeper increased the price of a product by 25% so that customer finds it difficult to purchase the required amount. But somehow the customer managed to purchase only 70% of the required amount. What is the net difference  in the expenditure on that product?

A) 10% more B) 5% more
C) 12.5% more D) 17.5% more
 
Answer & Explanation Answer: C) 12.5% more

Explanation:

    Quantity  X  Rate =  Price

 

         1  x  1  =  1

 

       0.7 x 1.25 = 0.875

 

      Decrease in price = (1-0.875) x 100 = 12.5%

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17 10727
Q:

133of 166of133of166 of 10000 of a number will be what percentage of that number?

 

A)  2.32 B)  1.32
C)  0.232 D) 0.0232
 
Answer & Explanation Answer: A)  2.32

Explanation:
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5 10568
Q:

Selling price of an article is Rs 2397 and discount offered is 15%. What is the marked price (in Rs)?

 

A) 2756.5 B) 2856.6
C) 2740 D) 2820
 
Answer & Explanation Answer: D) 2820

Explanation:
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10 10474
Q:

A farmer divides his herd of k cows among his 4 sons, so that one son gets one half of the herd, the second gets one-fourth, the third gets one-fifth and the fourth gets 9 cows. Then k is equal to ?

A) 160 B) 120
C) 140 D) 180
 
Answer & Explanation Answer: D) 180

Explanation:

Given total number of cows = k
Now, 1st son share = k/2
2nd son share = k/4
3rd son share = k/5
4th son share = 9

(k) + (k/4) + (k/5) + 9 = k
=> k - (19k/20) = 9
=> (20k-19k)/20 = 9
=> k = 180.

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17 10394