Percentage - 2

change = 100

error = 100• A = x % of B => if B = 100 then A = x• A = x % more than B => if B = 100 then A = 100 + x• A = x % less than B => if B = 100 then A = 100 – x• 100 % of any value is value itself.

Basics :

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1. A man is saving 33 ଵଷ of his income. If his income is increased by 25% and

expenditure is increased by 40%, then what is the % change in his savings?2. A student by mistake multiplied a number with ସ

ହ instead of multiplying with ହସ .

What is the % error in calculation?3. The population of a town is increasing by 20% every year. If the present

population of town is 72000, then what is the population of the town 2 years ago?

4. The price of the sugar is decreased by 30%. What is the % change inexpenditure if consumption is increased by 40% ?

5. In an examination, A boy scores 31% of max marks and fails by 12 marks. A girlscores 45%of max marks and pass by 16 marks. Find the max marks and the% required to pass?

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1. A man is saving 25% of his income. If his income is increased by 20%and expenditure is increased by 10%, then what is the % change inhis savings?

Ans :income = savings + expenditure100 25 75120 37.5 82.5

% change = 100= 50%

100 % = 75 10% = 7.5

% change in his savings = 50%COMSCIGUIDE

A student by mistake multiplied a number with instead ofmultiplying with . What is the % error in calculation?

2.

Let take a number which is multiplied by both numbersi.e. the lcm of two denominators. => lcm of (4,5) = 20

=> % error = 100= 36%

% error =ఱర

రఱఱ

ర100

= 36%

Ans : ସହ 20 = 16

ହସ 20 = 25

25 --- 16100 --- 64

36%% error in calculation = 36% COMSCIGUIDE

A student by mistake divided a number with instead ofmultiplying with 2. What is the % error in calculation?

2.

First convert both operations into one format ,the operation that we have to do on the number. Here it is multiplication.=> % error = 100

= 75%

% error =భమ 100

= 75%

Ans :

4 --- 1100 --- 25

75%

% error in calculation = 75% COMSCIGUIDE

The population of a town is increasing by 20% every year. If thepresent population of town is 72000, then what is the population ofthe town 2 years ago ?

3.

The population of the town is increasing every year. Before 2years it is less than the present population. the percentage improvement is 20 %

i.e one year later it will be ଵଶଵ present population

Similarly the population after 2 years will be ଵଶଵ

ଵଶଵ present population

Therefore 2 years ago the population will be ଵଵଶ

ଵଵଶ present population

Population 2 years ago = ଵଵଶ

ଵଵଶ 72000 = 50,000

Ans :

Population of the town 2 years ago = 50,000COMSCIGUIDE

The price of the sugar is decreased by 30%. What is the % change inexpenditure if consumption is increased by 40% ?

4.

Expenditure = consumption price10000 100 1009800 140 70

Ans :ଶଵ 100 = 2%

Method - 2

Method - 1

100 140 98

2% decrease

40 42 For method -2 assume initial amount as 100

% change in expenditure = 2%COMSCIGUIDE

In an examination, A boy scores 31% of max marks and fails by 12marks. A girl scores 45%of max marks and pass by 16 marks. Find themax marks and the % required to pass?

5.

Ans :

Maximum marks = 200% Required to pass = 37%

Max marks boys girls100 31 45

14% = 28 marks 1% = 2 marks 100% = 200 marks = maximum marks 12 marks = 6% and already boy has 31% 31+6 = 37%%required to pass is 37

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Problems for practice are given in the description of the video.

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Practice problemson Percentages

1. A train crosses a pole in 12 sec. It crosses a bridge of length 300m in 27sec. what is the time taken by the train to cross a bridge of length of 600m?

2. A train crosses a bridge of length 122m in 17 sec. it crossed another bridgeof length 210m in 25 sec. find the length of the train?

3. A train travelling at a speed of 54kmph crosses a platform in 36 sec and aman standing on the platform in 20 sec. find the length of the platform?

4. A train of length 240m travelling at a speed of 64kmph overtakes a manrunning at a speed of 10 kmph in __ sec ?

5. A train starts from a station X at 6am and reaches another station Y at 10am. Another train starts from station Y at 8am and reaches station ‘X’ at11:30am. At what time do the trains cross each other?

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The price of the sugar is increased by 25%. What is the % change inconsumption, if expenditure is increased by 50% ?

4.

Ans :

100 125 150

50% increase

25% x%

For method -2 assume initial amount as 100

ଶହଵଶହ 100 = 20%

% change in consumption = 20%COMSCIGUIDE

The value of a machine is decreases by 30% every year. If thepresent value of a machine is 1,47,000, then what is the value of themachine 2 years ago?

3.

The value of a machine before 2 years will be ଵ

ଵ present price

Value of a machine 2 years ago = ଵ

ଵ 1,47,000 = 3,00,000

Ans :

Value of the machine 2 years ago = 3,00,000

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A student by mistake multiplied a number with instead ofdividing with 3. What is the % error in calculation?2.

First convert both operations into one format ,the operation that we have to do on the number. Here it is multiplication.=>

% error = 100= -800%

Ans :

9 --- 1900 --- 100

-800% error in calculation = 800%COMSCIGUIDE

A student by mistake multiplied a number with instead of dividingwith . What is the % error in calculation?

2.

Error in calculation is zero Since multiplying with 2/5 is equal to dividing with 5/2

Ans :

% error in calculation = 0%COMSCIGUIDE

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