myhelper: SChand Composite Mathematics Class 7 Chapter 8 Ratio , Proportion , Unitary Method Exercise 8C

Exercise 8 C

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Question 1

100gm of butter make 14 cakes . How many cakes 150 gm make ?

Sol :

100gm of butter make= 14 cakes

1 gm------------=

$\frac{14}{100}$

150 gm ---------------------=

$\frac{14}{100} \times 150=21$ cakes

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Question 2

A plane flies 405 km on 90 liter of fuel .

(i) How much fuel is needed for 540km ?

(ii) How far can it go is 50 liters ?

Sol :

Plane files 405 km on = 90 liters

---------1 km ------- =

$\frac{90}{405}$

-------540 km ------=

$\frac{90}{405} \times 540$

=120 liters

(ii) In 90 liters it can fly = 405 km

-------1 liter --------- =

$\frac{405}{90}$

-------50 liters ------=

$\frac{405}{90} \times 50$

= 225km

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Question 3

16 articles cost Rs 72 . What will be the cost of 30 articles ? How many articles can be bought for Rs 207 ?

Sol :

16 articles cost = Rs 72

1 article cost =

$\frac{72}{16}$

30 article cost=

$\frac{72}{16} \times 30$ = Rs 135

(ii) In Rs 72 articles bought = 16

---Rs 1 ------------ =

$\frac{16}{72}$

----Rs 207 ---------=

$\frac{16}{72} \times 207$

= 46 articles

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Question 4

A Journey of 552 km takes 6 days. How long will a journey o f 1012 km take. If it is done at the same rate?

Sol :

A journey of 552 km takes = 6 days

-----------1km ------- =

$\frac{6}{552}$

--------------1012 km ---------=

$\frac{6}{552} \times 1012$

=11 days

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Question 5

Two and a half liters of paint is used to cover 725 sq m of area .

(i) How much will be required to paint 2001 sqm of area ?

(ii) How much area in sq m can be covered by 4.75 liters of paint?

Sol:

To cover 725 sq m area paint used = 2.5L

------------1 sq m --------=

$\frac{2.5}{725}$

------------- 2001 sq m ---------=

$\frac{25}{725} \times 2001$

= 6.9 L

(ii) 2.5 L point covers = 725sqm

1L --------------------=

$\frac{725}{2.5}$

4.75 ---------------=

$\frac{725}{25} \times \frac{4.75}{100} \times 10$

= 1377.5 sqm

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Question 6

$5 \frac{1}{4} m^{3}$ of copper sheet weight 1563kg. What will be weight of $3 \frac{1}{2} \mathrm{~m}^{3}$ of sheet ?

Sol :

$\frac{21}{4}$

$m^{3}$ weight = 1563

$m^{3}$ -------------=

$\frac{1563}{\frac{21}{4}}$

$\frac{7}{2} \mathrm{~m}^{3}$ weight =

$1563 \times \frac{4}{21} \times \frac{7}{2}$

= 1042 kg Answer

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Question 7

Harsh takes 150 steps in walking a distance of 125 meters .

(i) What distance would be cover in 360 steps?

(ii) How many steps would be needed to cover a distance of 120 m ?

Sol :

(i) Harsh takes 150 steps covers distance = 125 m

-----------------1 step ------------- =

$\frac{125}{150}$

------------360 steps-------------=

$\frac{125}{150} \times 360$

=300 m

(ii) 125 m distance covered in = 150 steps

1m ---------- =

$\frac{150}{125}$

120m -----------------=

$\frac{150}{125} \times 120$ = 144 steps

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Question 8

Fifteen chairs can be bought for Rs 3532.50 . How many chairs can be bought for Rs 5416.50 ?

Sol :

15 chairs can be bought for Rs 3532.50

Cost of Rs 3532.50 is = 15 chairs

---------Rs 1 ----------=

$\frac{15}{3532.50}$

Chairs bought for = Rs 5416.50 =

$\frac{15}{3532.50} \times 5416.50 .$

= 23 chairs Answer

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Question 9

45 packets of butter each weighing 100gm cost Rs 607.50 What be the cost of 18 packets of butter each weighing 500 gm ?

Sol :

If each packet weighting 100

Weight of 45 packets =

$45 \times 100=4500 \mathrm{gm}$

Weight 18 packets of each weight =

$18 \times 500$

$9000 \mathrm{gm}$

$4500 \mathrm{gm} \text { butter cost }=Rs 607.50$

1gm-----------

$=\frac{607.50}{4500}$

9000gm ------------ =

$\frac{607.50}{4500} \times 9000$

= Rs 1215 answer

SChand Composite Mathematics Class 7 Chapter 8 Ratio , Proportion , Unitary Method Exercise 8C

Exercise 8 C

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