From what I understand if we see someone's clock running slower than ours they will see ours running slower rather than theirs, but in my physics textbook they ask this question:
A spacecraft zooms past the Earth with a constant velocity. An observer on the Earth measures that an undamaged clock on the spacecraft is ticking at one- third the rate of an identical clock on the Earth. What does an observer on the spacecraft measure about the Earth-based clock’s ticking rate?
(a) It runs more than three times faster than his own clock.
(b) It runs three times faster than his own.
(c) It runs at the same rate as his own.
(d) It runs at one-third the rate of his own.
(e) It runs at less than one-third the rate of his own.
I thought the answer would be it runs one-third the rate of his own, but the correct answer (according to my book) is that it runs less than one-third the rate of his own. Is this correct? I don't know how to use the equations I've been given for special relativity to figure this out.