Question

Find the number of coins, 1.5 cm in diameter and 0.2 cm thick, to be melted to form a right circular cylinder of height 12 cm and diameter 4.5 cm.
pls, help.

Answer 1

Question :-

Find the number of coins, 1.5 cm in diameter and 0.2 cm thick, to be melted to form a right circular cylinder of height 12 cm and diameter 4.5 cm.

Given :-

• Diameter= 1.5cm & radius = 1.5/2 = 0 .75cm
• thickness (h) = 0.2cm
• melted in a cylinder of height = 12cm & diameter = 4.5cm, radius = 4.5/2 = 2.25cm
• Find number of coins = ?

Solution :-

• As the coins are in the form of thin cylinder
• Volume of each coin = πr²h

→  22/7 × (0.75)² × 0.2

→ 0.1125 π cm³

• Volume of melted cylinder = πr²h

→ 22/7 × (2.25)² × 10

→ 50.625 π cm³

number of coin required = volume of melted cylinder / volume of each coin

   

→ 50.625 π ÷ 0.1125 π

→ 450 coins

Hence :-

• Number of coins = 450 $\sf$

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