Question

I have two problems that I'm stumped on. I know the correct anwers but I'm having problems coming up with the co rrect anwsers. Here are the problems:

1) Magnesium has a density of 1.7g/cm^3 and iron has density of 7.9 g/cm^3. A block of iron has a mass of 819g. What is the mass of a block of magnesium that has the same volume as the block of iron?

I used the formula Density = Mass/volume x 1/0.001. My handout shows the answer as being 1.8 x 10^2g, but i can't get it using the above.

2) Calculate the number of cubic centimeters in a rectangular box 0.0385m long, 4.6cm wide, and 0.000078 km thick. I converted the "0.385m' TO 385, 0.000078km thick to 0.0078 and multiplied all numbers but again I'm stupmped. My handout shows the correct answer as being 14,000 cm^3.

What steps were taken to solve this problems?

Thanks!

Answer 1

massblock= 819g*1.7/7.9=1.8E2g

0.0385m= 3.85cm
.000 078km= .078m=7.8cm

I get volume to be 140cm^3