Finding the orbital period of a second planet using Kepler's third law

[OierL]

Homework Statement

In a distant galaxy, a planet orbits its sun at a distance of

m with a period of 108 s. A second planet orbits the same sun at a distance of

m. What is the period of the second planet?

Select one:
a.

s
b.

s
c.

s
d.

s
e.

Homework Equations

T^2=constant * r^3

The Attempt at a Solution

First of all I compute the constant whit the values of the first planet:
(108)^2 = const. * (1'8*10^12)^3 → const= 2*10^-33
Then, I compute the period of the second planet:
T^2 = 2*10^-33 * (9*10^11)^3 → T = √1458 = 38,18 s
This solution doesn't apear in the results I have to choose. What do I have wrong?

Thank you!

 

[phyzguy]

I suspect the period in the problem should read $10^8$s, not 108 s. 108s is an unphysical orbital period for a planet at this distance.

 

[OierL]

I suspect the period in the problem should read $10^8$s, not 108 s. 108s is an unphysical orbital period for a planet at this distance.

You are right! If I do the exercise with $10^8$s the result coincides with e.
Thank you very much!