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Overview: Percentages | CSAT Preparation - UPSC PDF Download

Introduction


  • The chapter on Percentages forms the most important chapter (apart from Number Systems) in the CAT syllabus and the XAT examination. The importance of ‘percentages’ is accentuated by the fact that there are many questions related to the use of percentage in all chapters of commercial arithmetic (especially Profit and Loss, Ratio and Proportion, Time and Work, Time, Speed and Distance). 
  • Besides, the calculation skills you develop while going through the chapter on percentages will help you handle Data Interpretation (DI) calculations. A closer look at that topic will yield that at least 80% of the total calculations in any DI paper constitute calculations on additions and percentage. 

Have a look at CAT 2019's question that is a mix of Percentages and Profit & Loss chapters:

  • CAT likes to mix the concepts in the questions. You can expect the same in CAT 2021 as well. That is the reason why you need good practice on questions to ace the Quant & DI section.
  • So how do you do that? - Don't worry, we have covered that for you at EduRev.

Definition

‘Percent’ as the name suggests ‘per’ means every and ‘cent’ means hundred i.e. “for every hundred”.

  • It is an important tool for the comparison of data and information.

Overview: Percentages | CSAT Preparation - UPSC

ExampleAna got 20 marks out of 40. Then, how many marks did she get when compared to 100?
Solution: By unitary method.

In the total of 40 marks, Ana got 20 marks Then,
In the total of 100 marks, Ana would have got = 20/40 *100 = 50 marks
It is just that when expressed in terms of hundred, it becomes percent.
That means to say Ana got 50%.

Concept of Percentage

  • A percentage can only be calculated if it has a base value or denominator.
  • In the above example, the base value or denominator was 40, which means to say that Ana secured 20 marks out of 40 (which is the base value of the calculation of marks secured.)
  • Concept of percent change = (Final value – initial value)/ initial value * 100

Overview: Percentages | CSAT Preparation - UPSC

Note: Initial value is taken as base or ‘denominator’ while calculating percent change.

Percent Point Change

  • It is very important to understand the difference between the percent change and percent point change.
  • Let us understand the difference between them by the following example:
    Ana secured 70 percent marks in her last term exam.
    Now, when we say that her marks increased by 5 percent, then this means that there is an increase of 5% marks when compared to the last marks she secured, which is 5% of 70% = 3.5%
    Her new secured marks will be 70 + 3.5 = 73.5%
    Now, when we say that her marks increased by 5 percentage points, then this means that there is an absolute increase of 5% marks in her marks, irrespective of the last marks she secured, which is her new secured marks will be 70 + 5% = 75%
    Therefore,

Percentage Point Change = Difference of two percentage figures

Overview: Percentages | CSAT Preparation - UPSC

Solved Examples

Example 1: A report consists of 20 sheets each of 55 lines and each such line consists of 65 characters. This report is reduced onto sheets each of 65 lines such that each line consists of 70 characters. The percentage reduction in the number of sheets is closest to:

Solution:

No. of Characters in one line = 65

No. of characters in one sheet = No. of lines × No. of characters per line = 55 × 65

Total number of characters = No. of sheets × No. of characters in one sheet = 20 × 55 × 65 = 71500

If the report is retyped:

New sheets have 65 lines, with 70 characters per line

No. of characters in one sheet = 65 × 70

Number of pages required:

Overview: Percentages | CSAT Preparation - UPSC

Hence, 16 pages will be required if the report is retyped.

Hence, reduction of (20 – 16) = 4 pages

% reduction is = (4/20) × 100 = 20% 


Question for Overview: Percentages
Try yourself:The number of votes not cast for the PNC Party increased by 25% in the National General Election over those not cast for it in the previous Assembly Polls, and the PNC Party lost by a majority twice as large as that by which it had won the Assembly Polls. If a total 2,60,000 people voted each time, how many voted for the PNC Party in the previous Assembly Polls?
View Solution


Example 2: 2/5th of the voters promise to vote for A and the rest promised to vote for B. Of these, on the last day, 15% of the voters went back of their promise to vote for A and 25% of voters went back of their promise to vote for B, and A lost by 200 votes. Then, the total number of voters is:

Solution:

Let x be the total number of voters.

Voters promised to A = 2/5 x

Voters backed out = 15% of 2/5 x

Voters promised to B = 3/5 x

Voters backed out = 25% of 3/5 x

Total Number of votes for A = (2/5x) – (15% of 2/5x) + (25% of 3/5x)

Overview: Percentages | CSAT Preparation - UPSC

Total Number of votes for B = (3/5x) – (25% 0f 3/5x) + (15% of 2/5x)

Overview: Percentages | CSAT Preparation - UPSC

Give Difference in votes is 200

Therefore,

Overview: Percentages | CSAT Preparation - UPSC

So, there were 10000 voters.


Question for Overview: Percentages
Try yourself:If the price of sugar goes up by 10%, then what should be the percentage decrease in the quantity consumed so that the total expenditure on sugar remains the same?
View Solution


Example 3. A person who has a certain amount with him goes to market. He can buy 50 oranges or 40 mangoes. He retains 10% of the amount for taxi fares and buys 20 mangoes and of the balance, he purchases oranges. The number of oranges he can purchase is:

Solution:

The person can buy 50 oranges or 40 mangoes.

Let the price of one orange be Rs. x

The total amount the person has = Rs. 50x

40 mangoes cost 50x, So one mango costs 1.25x

10% of the total amount is retained for taxi fare = 10% of 50x = 5x

20 mangoes bought for 20 * 1.25x = 25x

Money left with the person = 50x – (Taxi fare) – (Mangoes cost) = 50x – 5x – 25x = 20x

One Orange was for Rs. x, Therefore, 20 oranges can be bought with Rs. 20 x

Thus, the person bought 20 oranges.


Question for Overview: Percentages
Try yourself:Ramu conducts his business in the following manner : Every once in a while he raises his prices by a certain percentage and a while later reduces his price by the same percentage. After one such updown cycle of increasing and then decreasing his price by x%, the price of the commodity decreases by Rs 100. In the next cycle, he increases and decreases his price by (x/2)% and then sells the commodity for Rs 2376. What is the initial price of the commodity?
View Solution


Example 4. Forty percent of the employees of a certain company are men and 75% of the men earn more than Rs. 25,000 per year. If 45% of the company’s employees earn more than Rs. 25,000 per year, what fraction of the women employed by the company earned Rs. 25,000 or less per year?

Solution:

Let the total number of employees in the company be x

Then the number of men and women be 0.4x and 0.6x, respectively.

75% of men earn more than Rs. 25000 ⇒ 0.75 x 0.4 x = 0.3 x

Total number of employees earning more than Rs. 25000 = 45% x = 0.45 x

Number of women earning more than Rs. 25000 = Total employees earning more than Rs. 25000 – total number of Men earning more than Rs. 25000 = 0.45 x – 0.30 x = 0.15 x

Number of the women earning Rs. 25000 or less = 0.60 x – 0.15 x = 0.45 x

Fraction of the women employed by the company who earn Rs. 25000 or less = (0.45x/0.60x) = 45/60 = 3/4


Question for Overview: Percentages
Try yourself:PYQ (CAT 2019): On selling a pen at 5% loss and a book at 15% gain, Karim gains ₹ 7. If he sells the pen at 5% gain and the book at 10% gain, he gains ₹ 13. What is the cost price of the book in Rupees?
View Solution


Example 5: In a class of 60 students, 20% are male. 75% of female students passed an exam conducted for the whole class. What is the number of female students who passed the exam?

Solution: Since it is given that 20% of students are male, that means the remaining 80% are females.
Number of females - (80/100)*60 = 48
Number of female students who passed = 75% of 48 = 36 

The document Overview: Percentages | CSAT Preparation - UPSC is a part of the UPSC Course CSAT Preparation.
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FAQs on Overview: Percentages - CSAT Preparation - UPSC

1. What is the definition of percentages?
Ans. Percentages are a way of expressing a fraction or a portion of a whole in terms of parts per hundred. It is represented by the symbol "%", which is equivalent to dividing the given value by 100.
2. How is the concept of percentage used in everyday life?
Ans. The concept of percentage is used in various aspects of everyday life, such as calculating discounts during shopping, determining tax amounts, analyzing statistics and data, understanding interest rates, and evaluating changes in population or economic growth.
3. How can percentages be calculated?
Ans. Percentages can be calculated by dividing the part (the value of interest) by the whole (the total value) and then multiplying the result by 100. This will give the percentage value. Mathematically, it can be expressed as: Percentage = (Part / Whole) * 100.
4. Can percentages be added or subtracted?
Ans. Yes, percentages can be added or subtracted. When adding or subtracting percentages, it is important to convert them into their decimal form first. Adding percentages involves finding the sum of the individual percentages, while subtracting percentages involves finding the difference between them.
5. How can percentages be used to solve real-life problems?
Ans. Percentages are widely used in solving real-life problems, such as calculating discounts, determining markups and profits, analyzing data and statistics, understanding population growth or decline, and evaluating changes in interest rates or inflation. By applying the concept of percentages, one can make informed decisions and understand various aspects of the world around us.
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