In this resource the time is given for a train to pass a signal. The time is also given for a train to completely pass through a tunnel. It is assumed that the train is travelling at constant speed. The task is to calculate the length of the train.
Solving the problem requires the use of the formula for speed, along with some algebraic manipulation of fractions.
The ‘something in common’ between each of the 16 examples is that the length of the train is always half the length of the tunnel. Looking at the mathematics behind why this is so involves using algebraic fractions and factorisation.