SChand Composite Mathematics Class 7 Chapter 9 Percentage and it's application Exercise 9B

  Exercise 9B

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Q1 | Ex-9B | Class 7 | SChand Composite Maths | Percentage and it's application | myhelper

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Question 1 

Fill in the blanks

(i) 23% + 47% + ___ =100%

(ii) 54% = 100% - ___ 

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Question 2

18% of 650 boys in a school take commerce. How many boys take commerce?

Sol :

Boys take commerce=18% of 650

$=\frac{18}{100} \times 650=117$ boys

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Question 3

Certain cereals contains 12% of protein. How many grams of protein is there in a 14g package?

Sol :

Protein in cereals = 12% of 14

$=\frac{12}{100} \times 14=\frac{168}{100}$

=1.68 g

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Question 4

There are 160 pages in a book 15% of the pages have pictures on them. How many pages do not have pictures on them?

Sol :

If 15% pages have pictures then pages which do not have pictures=100%-15%=85%

Number of pages do not have picture=85% of 160

$=\frac{85}{100} \times 160=136$ pages

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Question 5

When making a Journey I walked 12%, ran 16% and rode on scooter 28% of the total distance and for the remaining part, I travelled by bus. How many km did I travel by bus If the total distance covered was 50km?

Sol :

Journey by walk , ran , scooter=12% + 16%+23%

=56%

Journey by bus=100-56=44%

Distance covered by bus=44% of 50

$=\frac{44}{100} \times 50$

=22 km

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Question 6

(i) Out of every 20 vehicles passing  a certain spot 7 were bus. What percentage was this?

Sol :

$=\frac{7}{20} \times 100$

=35%

(ii) Out of 400 tickets sold at a tennis matches 144 were sold to senior citizens. What percent of the tickets were sold to senior citizens ? What percentage were sold to the rest?

Sol :

Total tickets = 400

Tickets to senior citizens=144

Tickets to rest = 400 - 144 =256

Percentage of senior citizens 

$\frac{144}{400} \times 100$

=36%

Percentage of rest citizens

$\frac{256}{400} \times 100$

=64%

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Question 7

You spend $7\frac{1}{2}$ hours out of 24 hours at school. What percentage of a day is this ?

Sol :

Percentage of the day$=\frac{7.5}{24} \times \frac{100}{10}=\frac{375}{12}$

=31.25%

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Question 8

A certain alloy consists 3 part of tin to 5 parts of copper. What is the percentage compositing on the alloy?

Sol :

Ratio of tin to copper in alloy= 3 : 5

Total alloy = 3+5 =8

Percentage of tin in alloy $=\frac{3}{8} \times 100$

=37.5%

Percentage of copper in alloy $=\frac{5}{8} \times 100$

=62.5 %

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Question 9

The price of a muffin increases from 4 to 5 . Wat is the percentage increase?

Sol :

Increase in price = 5-4 =1

Percentage $=\frac{\text{increase}}{\text{original}} \times 100$

$=\frac{1}{4} \times 100$

=25%

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Question 10

The number of people employed in firm decreased from 240 to 210. Find the percentage decrease.

Sol :

Decrease = 240- 210=30

Decrease percentage $=\frac{30}{240} \times 100$

= 12.5%

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Question 11

The speed of a train is 80 km/hr .

(i) It is increased to 130 km/hr . Find percentage increase.

Sol :

Increase = 130 - 80 = 50 km/hr

Percentage Increase $=\frac{50}{80} \times 100$

=62.5 %

(ii) Decreased to 65 km/hr . Find percentage decreased .

Sol :

Decrease = 80 - 65 =15

Percentage Decrease $=\frac{15}{80} \times 100$

=18.75%

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Question 12

A four meter elastic band is increased by 10%. Find its new length.

Sol :

Increase = 10% of 4

$=\frac{10}{100} \times 4$

=0.4 m

New length = Original + Increase 

=4+0.4=4.4 m

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Question 13

The length of a rope is decreased by $12\frac{1}{2}$ % . What is the length if its was 150 m ?

Sol :

Decrease = 12.5 % of 150

$=\frac{125}{100} \times \frac{150}{10}$

$=\frac{75}{4}$

=18.75

New length = 150 - 18.75 =131.25

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Question 14

The monthly expenditure of a family on milk is 700 . If the price of the milk is increased by 8% . Find the increase in the expenditure of the family on milk.

Sol :

Increase = 8% of 700

$=\frac{8}{100} \times 700$

=56

Increased expenditure = 700 + 56

=756

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Question 15

The population of an Indian State is 8 crore . If it is increased by 2% every year, find the population of the state after one year.

Sol :

Population = 8 crore 

Increase by = 2% of 80000000

$=\frac{2}{100} \times 80000000$

=1600000

New population

=800000000+1600000

=81600000 or 8.16 crore

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Question 16

A company used 75% of its profits to buy new machinery and raw materials. If this amounted to 85071. Find the total profits of the company.

Sol :

Total Profit = 100%

Invested  75%=85071

$1\%=\frac{85071}{75}$

$100\%=\frac{85071}{75} \times 100$

=113428

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Question 17

A man left 25% of his money to his mother, 55% to his daughter and the remaining 9000 to his brother. How much money did he leave ? Find the shares of his mother  and daughter.

Sol :

Let the man  have 100% of money 

He gives to mother , daughter=25+55=80%

Remaining gives to his brother=100-80=20%

According to question,

20% = 9000

then $1\%=\frac{9000}{20}$

∴$100\%=\frac{9000}{20} \times 100=45000$

Mother's share = 25% of 45000

$=\frac{55}{100} \times 45000$

=24750