Where Did I Go Wrong in Calculating the Proton's Re-emergence Time?

[ahazen]

A proton (mass= 1.7×10-27 kg, charge= 1.6×10-19 C) traveling with speed 106 m/s enters a region of space containing a uniform magnetic field of 1.2 T.
What is the time t required for the proton to re-emerge into the field-free region?

I plugged the numbers into r=mv/qB and then t=pi r/ v

I got 2.7815 e-18 but the homework online says I am off by a power of ten.
Anyone know where I went wrong?
Thank you:)

 

[Stonebridge]

I get 2.8 x 10^-8s [to 2 sig figs]
Without seeing your calculation I don't know where you went wrong.
The method is correct. Just check your powers of 10 again.

 

[ahazen]

Thank you so much for all your help:) The homework online says your answer is correct:)