A train takes a quarter of a minute to pass a sign. It then passes through a tunnel, taking three quarters of minute to do so. The tunnel is six hundred metres long. The train had a constant speed for all that time.
How fast was the train going?
A: Fifty kilometres per hour
B: Fifty-Six kilometres per hour
C: Sixty-Four kilometres per hour
D: Seventy-Two kilometres per hour
E: Eighty-Four kilometres per hour
Give it a crack.
Answer to come later if no-one gets it.
(This was a question I half remember from the Australian Mathematics Competition Thursday of this week).