Copyright © University of Cambridge. All rights reserved.
The Red Express Train usually has five red carriages, but so many people wanted to catch it one weekend the station manager had to add two blue carriages.
At first she thought to put them both on the end, then at the front, then one on each end - but wasn't happy with any of those. So she thought about other ways to put the blue carriages into the train. How many ways can you find?