Satnav Dilemma
How many routes are there in this diagram from S to T?
How many different routes are there from S to T which do not go through either of the points U and V more than once?
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![Satnav Dilemma Satnav Dilemma](/sites/default/files/styles/large/public/thumbnails/content-id-2411-WP31Qa.gif?itok=q27iZJ_x)
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
There are 3 routes from S to U and 2 from U to V. The number of different routes from S to T is therefore 3 x 2 =6. Each of these can be followed by any one of three different routes from V to T, making a total of 6 x 3 = 18 routes in all.