Exercise 9 B
Question 1
Fill in the blanks:
(i) $23 \%+47 \%+ 30%=100 \%$
(ii) $54 \%=100 \%-46 \%$
Question 2
18% OF 650 Boys in a school take commerce . How many boys take commerce?
Sol: Boy take commerce = $18 \%$ of 650
$=\frac{18}{100} \times 650=117$ boys
Question 3
Certain cereals contains 12% of protein . How many grams of protein is there in a 14 g package ?
Sol: Protein in cereals = 12% of 14
$=\frac{12}{100} \times 14=\frac{168}{100}$
$=1.68 \mathrm{~g}$
Question 4
There are 160 pages in a book . 15% Of the pages have picture on them. How many pages do not have pictures on them?
Sol: If 15 % pages have pictures then pages do not have pictures= $100 \%-15 \%=85 \%$
Number of pages do not have pic = 85% of 160
$=\frac{85}{100} \times 160=136$ Pages
Question 5
When making a Journey I walked 12% run 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 50 km?
Sol: Journey by walk, run , scooter $=12 \%+16 \%+23 \%$
$=56 \%$
Journey by Bus = 100-56= 44%
Distance covered by bus = 44% of 50
$=\frac{44}{100} \times 50=22 \mathrm{~km}$
Question 6
(i) Out of every 20 vehicles passing a certain speed 7 were buses. what percentage was this?
Sol: $\frac{7}{20} \times 100=35 \%$
(ii) Out of 400 tickets sold at a tennis match, 144 were sold to senior citizens what percent of the ticket were sold to senior citizens?
Sol: Total tickets = 400
Tickets to senior citizens= 144
Tickets to rest = 400- 144= 256
% of senior citizens = $\frac{144}{400} \times 100=36 \%$
% of rest citizens = $\frac{256}{400} \times 100=64 \%$
Question 7
You spend $7 \frac{1}{2}$ hours out of 24 hours at school what percentage of a day is this ?
Sol: = % $\frac{7 .5}{24} \times \frac{100}{10}=\frac{375}{12}=31.25 \%$
Question 8
A certain alloy consists 3 part of tin to 5 parts of copper. What is the percentage composition of the alloy ?
Sol: Ratio of tin to copper in alloy = 3:5
Total alloy = 3+5 = 8
% of tin in alloy =$\frac{3}{8} \times 100=37.5 \%$
% of copper in alloy = $\frac{5}{8} \times 100=62.5 \%$
Question 9
The price of a muffin increase from Rs 4 to Rs 5 what is the percentage increase ?
Sol: Increase in price = 5-4 = Rs 1
% Increase = $\frac{\text { increase }}{\text { original }} \times 100=\frac{1}{4} \times 100=25 \%$
Question 10
The number of people employed in firm decreased from 240 to 210 . find the percentage decrease
Sol: Decrease = 240 - 210 = 30
% Decrease = $\frac{30}{240} \times 100=12.5 \%$
Question 11
The speed of a train is 80 km\hr . If is
(i) Increased to 130 km\hr . Find % increase
Sol: Increase = $130-80=50 \mathrm{~km} / \mathrm{hr}$
% Increase = $\frac{50}{80} \times 100=62.5 \%$
(ii) Decreased to 65 km\hr . find % decrease .
Sol: Decreased = 80-65 = 15
% Decreased = $\frac{15}{30} \times 100=18.75 \%$
Question 12
A four meter elastic band is increased by 10% find its new length .
Sol: Increase = 10% of 4 =$\frac{10}{100} \times 4=0.4 \mathrm{~m}$
New length = Original + Increase
= $4+0.4=4.4 \mathrm{~m}$
Question 13
The length of a rope is decreased by $12 \frac{1}{2} \%$ what is the length if it 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
Question 14
The monthly expenditure of a family on milk is Rs 700. If the price of the milk is increased by 8% . Find the increase in the expenditure of the family on milk .
Sol: Old expenditure = 700
Increase = 8% of 700 = $\frac{8}{100} \times 700=Rs 56$
Increase expenditure= 700 + 56 =Rs 756
Question 15
The population of an India state is 8 crore. If it increase 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 = $80000000+1600000$
= 81600000 or 8.16 crore
Question 16
A company used 75 % of its profits to buy new machinery and raw materials. IF this amounted to Rs 85071. Find the total profit of the company.
Sol: Total profit = 100%
Invested = 75% = 85071
1% = $\frac{85071}{75}$
100% =$\frac{85071}{75} \times 100$
= Rs 1,13,428 answer
Question 17
A man left 25 % of his money to his mother, 55 % to his daughter and the remaining Rs 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%
Acc to question 20%= 9000
Then 1% = $\frac{9000}{20}$
$\therefore \quad 100 \%=\frac{9000}{20} \times 100=45,000$
Mother's share = 25% of 45000
$=\frac{25}{100} \times 45000$
= Rs 11250 Answer
Daughter share = 55% of 45000
$=\frac{55}{100} \times 45000$
= Rs 24750 Answer
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