Question

find the least number of coins of diameter 2.5 cm and height 3mm which are to be melted to form a solid cylinder of radius 3 cm and height 5 cm​

Answer 1

96 coins which are to be melted to form a solid cylinder.

let number of coins is n.

here coins are to be melted to form a solid cylinder.

so volume of cylinder = n × volume of each coin

⇒πR²H = n × πr²h

⇒(3cm)² × (5cm) = n × (2.5/2 cm)²(3mm)

⇒9 × 5 cm³ = n × 5/4 × 5/4 × 0.3 cm³

⇒45 = n × 25/16 × 0.3

⇒n = 45 × 15/(25 × 0.3) = 96

hence number of coins is 96.

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Answer 2

Answer:

let number of coins is n.

here coins are to be melted to form a solid cylinder.

so volume of cylinder = n x volume of each coin

→πR²H = n x r²h

(3 cm)2 * x (5cm) = n x (2.5/2 cm)?(3mm) 9 x 5 cm3 = n x 5/4 x 5/4 x 0.3 cm3

45 = n x 25/16 x 0.3

an = 45 x 15/(25 x 0.3) = 96 hence number of coins is 96.