Vol of first coin = (pi)(15/2)^2 * 2 = [(pi)(15)^2]/2 = v/2

vol of Aluminium = vol of Silver = v/4
2* wt of Aluminium (a) = wt of silver(s) = 2s
s = 2a

2a + a = 30
a for v/4 = 10gm


vol of sec coin = (pi)(30/2)^2 * 1 = v
a for v/4 ==> 10gm
a for v ==> 40 gm

Option B

Volume of the cylinder = pi*r*r*h (where r = radius of the cylinder and h = height of the cylinder)

Volume of cylinder UNO = pi *15*0.5*15*0.5*2
Volume of Silver in cylinder UNO = pi *15*0.5*15*0.5
Volume of Aluminium in cylinder UNO = pi *15*0.5*15*0.5

Let Ds, Da be the densities of Silver and Aluminium respectively and Ds = 2*Da(silver is twice heavier than aluminium), So

Weight of Silver in cylinder UNO = pi *15*0.5*15*0.5*Ds = pi *15*0.5*15*0.5*2*Da (Weight = Volume * Density)
Weight of Aluminium in cylinder UNO = pi *15*0.5*15*0.5*Da
Total Weight of of the cylinder UNO = pi *15*0.5*15*0.5*Da + pi *15*0.5*15*0.5*2*Da = 30

pi *15*0.5*15*0.5*3*Da = 30

Volume of cylinder DOS = pi *15*15*1
Volume of Silver in cylinder DOS = 0
Volume of Aluminium in cylinder DOS = pi *15*15*1


Weight of Silver in cylinder DOS = 0
Weight of Aluminium in cylinder DOS = pi *15*15*Da
Total Weight of of the cylinder DOS = pi *15*15*Da = ?

pi *15*0.5*15*0.5*3*Da = 30
pi *15*15*Da = 30/(0.5*0.5*3) = 40

IMO Answer B

i didnt quite get why did you divide v/2 and then later V/4, volume of alloy