Question

Find the number of coins each 2.4 cm in diameter and 2 mm thick, to be melted to form a right circular cylinder of height 12 cm and diameter 6 cm.​

Answer 1

Answer:

Diameter of coin = 2.4 cm

Radius of coin =\frac{2.4}{2}=1.2 cm

2

2.4

=1.2cm

Thickness of coin = 2mm = 0.2 cm

Volume of coin = \pi r^2 h = \frac{22}{7} \times (1.2)^2 \times 0.2πr

2

h=

7

22

×(1.2)

2

×0.2

Height of cylinder = 12 cm

Diameter of cylinder = 6 cm

Radius of cylinder = \frac{6}{2}= 3 cm

2

6

=3cm

Volume of cylinder =\pi r^2 h = \frac{22}{7} \times 3^2 ( 12)πr

2

h=

7

22

×3

2

(12)

We are given that number of coins 2.4cm diameter and 2mm thick, to be melted ti form circular cylinder of height 12cm and diameter 6cm

So, No. of coins = \frac{\frac{22}{7} \times 3^2 ( 12)}{\frac{22}{7} \times (1.2)^2 \times 0.2}=375

7

22

×(1.2)

2

×0.2

7

22

×3

2

(12)

=375

Hence 375 coins to be melted to form circular cylinder