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Question
How many coins 1.75cm in diameter and 2mm thick must be melted to form a cuboid 11cm x 10cm x 75cm___?
Solution
Given that dimensions of a cuboid 11cm x 10cm x 75cm
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
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