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A grocer places some oranges, peaches, apples and bananas in a row so that, somewhere in the row each type of fruit can be found next to each other type of fruit. What is the smallest possible number of fruits in the row?

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.

*This problem is taken from the UKMT Mathematical Challenges.**View the archive of all weekly problems grouped by curriculum topic*