Help with my physics homework please

[madman555]

Homework Statement

How long would it take a radio wave whose frequency is 7.25 x 10^5 Hz to travel from Mars to Earth if the distance between the two planets is approximately 8.00 x 10^7 km.

Homework Equations

Don't know what to put here.

The Attempt at a Solution

7.25 x 10^5 / 8.00 10^9=9.0625 x 10^-5
Is that they right answer or am i doing this whole thing the wrong way?

 

[berkeman]

Homework Statement

How long would it take a radio wave whose frequency is 7.25 x 10^5 Hz to travel from Mars to Earth if the distance between the two planets is approximately 8.00 x 10^7 km.

Homework Equations

Don't know what to put here.

The Attempt at a Solution

7.25 x 10^5 / 8.00 10^9=9.0625 x 10^-5
Is that they right answer or am i doing this whole thing the wrong way?

Hint: The frequency of the radio wave is irrelevant in this question. What is the velocity of propagation of light (and hence radio waves) in a vacuum?