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 10 cm and diameter 4.5 cm.

Explanation

Given that,lots of metallic circular disc to be melted to from a right circular cylinder.Here, a circular dis work as a circular cylinder.
Base diameter of metallic circular diss = 1.5 cm
`therefore` Radius of metallic circular dis `= (1.5)/(2) cm" " [ because "diameter" = 2xx "radius"]`
and height of metallic circular disc i.e., = 0.2 cm
`therefore` Volume of a circular disc `= pi xx ("Radius")^(2) xx "Height"`
`" " pixx ((1.5)/(2))^(2) xx 0.2`
`" "= (pi)/(4) xx 1.5 xx 1.5 xx 0.2`
Now, height of a right circular cylinder (h) = 10 cm
and diameter of a right circular cylinder = 4.5 cm
`therefiore ` Volume of right circular cylinder (r) `= (4.5)/(2) cm `
`rArr` Radius of a right cicrular cylinder `= pir^(2) h`
`" " = pi ((4.5)/(2))^(2) xx 10 (pi)/(4) xx 4.5xx 10`
`therefore "Number of metallic circular disc "= ("Volume of a right cicrular cylinder")/("Volume of a metallic circular disc")`
`" "= ((pi)/(4) xx4.5 xx 4.5xx10)/((pi)/(4) xx 1.5xx 1.5xx 0.2)`
`= (3xx3xx10)/(0.2) = (900)/(2) = 450 `
Hence, the required number of metallic circular disc is 450.