Crossing the River

Aims and objectives
This is a problem solving activity based on the traditional ‘foxes and chickens’ conundrum where pupils are encouraged not only to solve the problem using a variety of permutations but also to try and work out the underlying mathematics.

Previous knowledge
This is a ‘logic’ problem solving game so no prior learning is needed however for pupils to solve the mathematics then a basic understanding of algebra would be helpful.

In the classroom
This activity is based on the traditional foxes and chickens conundrum. The student has to solve the problem of transporting a set of young and adult monkeys from one side of the river to the other using a floating log. The log, however, can only hold one adult or up to two young monkeys at any one time.

Once the initial activity has been completed, feedback is provided on the number of trips taken which is then compared to the minimum number required. The student can then elect to play again to improve upon the number of trips taken or change the combination of monkeys to make the problem solving more complex. They can do this by clicking on the 'Set Puzzle' button.

At the end of each problem there is a prompt to encourage the student to try and work out the mathematics behind the activity. The pupil can then change the number of monkeys to test their hypothesis. There are hints provided to help the student work out how many trips 'n' monkeys would take (the answer is also available if needed).

Used with an interactive whiteboard in a whole class or large group situation, stimulating and lively debate can ensue which provides a useful insight into pupils’ approaches to problem solving.

 Support materials description: Resources type: The crossing_the_river.pdf contains a set of graphics (background, seven large and ten small monkeys) which can be printed off onto stiff paper or card. This can be laminated and the pictures cut out to create a permanent desk-based version of the activity. crossing_the_river.pdf

Curriculum references
Mathematics – KS3:
Ma2: 1a, i, j, k
Ma2: 5a, b, d