Question

The mass of a silver plate is directly proportional

to its volume. When its volume is 20 cm3, its
mass is 210 g.
(a) Find the mass of a silver plate of volume
50 cm3
(b) If the mass of a plate is 399 g, what is
its volume?

Answer 1

(a) 525 g

Since they're proportional to each other:

`(20cm^(3) )/(210g) =(50cm^(3) )/(Xg)`

Cross-multiply & solve:

`20x=210*50\\20x=10500\\x=(10500)/(20) =525`

(b) 38 cm^3

Same thing, different numbers:

`(20cm^(3) )/(210g) =(Xcm^(3) )/(399g)`

Cross-multiply & solve:

`210x=20*399\\210x=7980\\x=(7980)/(210) =38`