Volume of block given underwater and land weight

[test2morrow]

Homework Statement

A block of metal weighs 9N in air and 7N in water. What is volume of block?

correct answer: 200cm^3

Homework Equations

w=mg
d=m/v

The Attempt at a Solution

I figured out that it has mass of 0.9kg on land...which may or may not be helpful.

 

[bucher]

You know the difference in weights of the block when in different mediums. This is a buoyancy problem. The difference in weights is equal to the weight of water displaced by the block. If you use the density of water with the weight of water displaced you'll get the volume of the block.

 

[test2morrow]

thanks!