Question

A metallic sphere is made of an alloy of two metals 'P
and 'Q'having specific gravities (or relative densities)
20 and 2, respectively. The sphere weighs 120 gwt in
air and 90 gwt in water. Find the percentage of the
mass of metal 'P' in the alloy.​

Answer 1

Answer:

Difference in weight of sphere in air and water is 120-90 = 30 gwt  

So volume of metallic sphere is 30gwt

Assume

Volume of P in the alloy = A

From definition of density

mass = density x volume

mass of P in the alloy = 20 A

Volume of Q = 30 - A

Mass of Q in alloy = 2 (30 - A)

Then total mass of alloy = 20 A + 2 (30 -A)

120 = 20 A + 60 - 2A

60 = 18A

A = 3.33

Volume of P = 3.33 cm3

Mass of P = 3.33 x 20 = 66.66 g

 

% mass of P = mass of P * 100/ mass of alloy

= 66.66 * 100/120  

= 55.55%

Explanation:

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