Question

How many coins 1.75 cm in diameter and 2 mm thick must be melted to form a cuboid 11 cm × 10 cm × 7 cm?

Answer 1

Given that dimensions of a cuboid 11cm x 10cm x 7cm

So its volume (V₁) = 11cm x 10cm x 7cm

= 11 x 10 x 7cm³         ..........(1)

Given diameter (d) = 1.75cm

Radius (r)`=d/2=1.75/2=0.875cm`

Thickness (h) =2mm = 0.2cm

Volume of acylinder =`pir^2h`

`V_2=pi(0.875)^2(0.2)cm^3`   ........(2)

V₁ = V₂ x n

Since volume of a cuboid is equal to sum of n volume of ‘n’ coins

`n =V_1/V_2`

n = no of coins

`n=(11xx10xx7)/(n(0.875)^2(0.2))_`

n = 1600

∴No of coins (n) = 1600