Question

Find the number of coins, 1.5 cm in diameter and 2 mm thick, to be melted to form a right circular
cylinder of radius 2.25 cm and height 10 cm.​

Answer 1

Answer:

450

Step-by-step explanation:

Given--->

----------

Thickness of coin= 2mm

= 2/10 cm

= 0.2 cm

Diameter of coin = 1.5 cm

radius of cylinder formed =2.25 cm

Height of cylinder =10 cm

To find ---> Number of coins melted to

-----------

form cylinder of given height and radius

Solution-->

-------------

Coin is also cylindrical shape

Volume of one coin=π r² h

=π (1.5/2)² ×0.2

=π (0.75)²× 0.2 cm³

Let n coin be melted to form new cylinder

Volume of n coin= n ×π ×0.75×0.75×0.2

Volume of new cylinder=πr²h

=π(2.25)²×10

Volume of n coins = Volume of cylinder

n×π×0.75×0.75×0.2 = π ×2.25×2.25×10

π cancel out from both sides

n=2.25 × 2.25 × 10 /0.75 × 0.75 × 0.2

n =3 × 3 × 100 / 2

= 9 × 50

n =450

So 450 coins to be melted to form cylinder

Additional information--->

------------------------------------

1)Curved surface area = 2π r h

2)Total surface area= 2πr(r + h)

3)Area of base of cylinder=π r²

4)Volume of cone=1/3 π r² h

5)Curved surface area=π r l

6)Total surface area = π r (r + l)

Answer 2

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450

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