Two trains are approaching each other on a long straight section of track. One train is going 5 kilometres per hour and the other is going 3 kilometres per hour. At the time when the trains are 3 kilometres apart a mosquito starts flying from the front of the slower train towards the faster train. When it reaches the faster train it immediately turns around and flies back towards the slower train. If the trains are one kilometre apart when the mosquito first returns to the slower train, what is the speed at which the mosquito is flying, measured in kilometres per hour?
