Question

the number of coins, each of radius 0.75cm and the thickness 0.2cm, to be melted to make a right circular cylinder of height 8cm and base radius 3cm?

Answer 1

Answer:

The number of coins, each of radius 0.75 cm and thickness 0.2 cm, to be melted to make a right circular cylinder of height 8 cm and radius 3 cm is. 640. 600.

Answer 2

GIVEN :

$\sf \bullet$ Coins are melted to form right circular cone

$\sf \bullet$ Radius of coin = 0.75cm

$\sf \bullet$ Thickness of coin = 0.2 cm

$\sf \bullet$ Height of right circular cone = 8cm

$\sf \bullet$ Base radius of right circular cone = 3cm

TO FIND :

Number of coin to be melted

FORMULA USED :

$\sf \bullet$ Volume of cylinder = πr²h

$\sf \bullet$ Volume of cone = (1/3)πr²h

SOLUTION :

Coins are in shape of cylinder.

These Coins are melted to form right circular cone.

Therefore, volume of right circular cone = Volume of coins melted

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$\sf \implies \: Volume \:of \:one\: coin \:= \: 3.14 \times (0.75 cm)^2 \times 0.2cm\\\\\sf \implies \: Volume \:of \:one\: coin \:= \: 0.628 \times 0.5625 \: cm^3\\\\\sf \implies \: Volume \:of \:one\: coin \:= \: 0.35325 cm^3$

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$\sf Volume \:of \:right\: circular\: cone \:= \:\dfrac{1}{3} \times \pi \times {(3\:cm)}^2 \times 8cm\\\\\sf \implies \:Volume \:of \:right\: circular\: cone \:= \dfrac{1}{3} \times 3.14 \times 9 \times 8 cm^3\\ \\\sf \implies \: Volume \:of \:right\: circular\: cone \:= \: 3.14 \times 3 \times 8 cm^3\\\\\sf \implies \: Volume \:of \:right\: circular\: cone \:= \: 75.36 cm^3$

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Now ,

Number of coin melted × Volume of one coin = Volume of right circular cone formed

➝ Number of coin melted × 0.35325 cm³ = 75.36 cm³

➝ Number of coin melted = 75.36 ÷ 0.35325

➝ Number of coin melted = 213.33

➝ Number of coin melted ≈ 213

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ANSWER : 213 coins