# Is there a typo in this time dilation problem?

I am looking at a special relativity question but none of the choices make sense. If a clock is racing by you at the speed 45 of light speed and you determine that 30 minutes go by on the clock, how many minutes will have gone by on your own clock? The choices are as follows:

My attempt: $$\Large t' = \frac{t}{\sqrt{1-\frac{v^2}{c^2}} }$$Then plugging in$$\frac{30}{\sqrt{1-\frac{(.45c)^2}{c^2}} }= 33.59$$ Converting minutes to seconds doesn't change the answer.

The answer is supposed to be $50$ minutes.

If you were forced to choose one of the provided answers, you should of course choose (d), however. You can eliminate (a) and (b) because you know their clock is dilated relative to yours. Similarly, you can eliminate (c) because at speed $0.45c$, some dilation will occur. So speaking strictly conceptually, choice (d) is the only possible answer (although it is far too high).
• Thank you for your response. Can you also look over my work on a similar problem. A clock moves past you at a speed of 0.9 How much time passes for you for each second that elapses on the moving clock? I got $t= \frac{1}{ \sqrt{ 1 - \frac{(.90c)^2}{ c^2}}} (1) = 2.29~ {\rm sec}$ – john Dec 31 '17 at 21:47