Two Chemistry problem on density?

Question

1) A cylindrical column of mercury has a mass of 242.3346 grams and has a diameter of 1.250cm and has a height of 14.52cm. Calculate the density of mercury.

#2 ) A student determines the mass of a bone to be 23.3751 grams. A 50mL graduated cylinder contains 30.3 mL of water. When the bone is placed in the water-filled cylinder, the water level rises to 42.6mL. What is the density of bone?

I'm having a hard time with these problem so I would appreciate any help. I know its really easy but I don't think my answers are right.

Answer 1

density is mass per volume.

for both of these you have the mass already

1 cubic centimetre is 1mL

for the first one: area of circle x height of tube = volume

so mass / volume =???

for the second: objects displace their volume when put into water if completely submerged (which we have to assume it is).

subtract initial volume from final volume (42.6-30.3)

then mass / volume = ???

water has density of 1kg/L (==1g/mL)

mercury has much higher than that, and i would say from those numbers that the bone does too (23.3751/12.3 =~2)

Answer 2

Density= mass/volume

1.) mass of mercury in the tube: 242.3346g

     volume of the column: pi*1.250/2*14.52= 28.51 cm^3= 28.51 mL

     242.3346g/28.51mL= 8.500g/mL

2.) Given: mass of bone 23.3751g

               volume of bone- 42.6-30.3=12.3 mL

    23.3751g/12.3mL= 1.90g/mL