Density of a platinum-iridium cylinder

[Minihoudini]

Homework Statement

The standard kilogram is a platinum-iridium cylinder 39.0 mm in height and 39.0 mm in diameter. What is the density of the material?

Homework Equations

now I know that to find volume you have to use v=h(pi)r^2
and I also know you have to convert it to meters. When I do I get this
(0.039)(pi)(0.0195)^2
which gives me 4.6589033654573236278091385713189e-5
so this is what I get over all
1 / (39.0 * pi * (19.5^2)) = 2.14642786 × 10-5
yet the answer is 2.15*10^4k/m^3
can someone tell me what I am doing wrong, and if I am suppose to convert the 2.14

The Attempt at a Solution

 

[Astronuc]

Well, 2.1464 is rounded up to 2.15 if one is using three significant digits in the final answer.

One's solution is correct, the density is about 21464 or approximately 21500 kg/m³

 

[MAR12]

That answer is correct but be careful with units. 21464 is in millimeters. so it would be 21.464 kg/m^3

 

[rl.bhat]

1 / (39.0 * pi * (19.5^2)) = 2.14642786 × 10-5

This step is wrong. It should be
1 / (0.0390 * pi * (0.195^2)) = 2.14642786 × 10^4