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Age 14 to 18
Challenge Level Yellow star
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Why do this problem?
The problem gives practice in solving linear and quadratic inequalities.

Possible approach
Use this as a lesson starter. If learners do not know how to start let them use the Hint.

Then discuss the problem as a class but try to elicit ideas from the learners themselves.

Key questions
How do we make use of the information given?

If we are not making progress, then have we used all the information given?



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Shades of Fermat's Last Theorem

The familiar Pythagorean 3-4-5 triple gives one solution to (x-1)^n + x^n = (x+1)^n so what about other solutions for x an integer and n= 2, 3, 4 or 5?

Two Cubes

Two cubes, each with integral side lengths, have a combined volume equal to the total of the lengths of their edges. How big are the cubes? [If you find a result by 'trial and error' you'll need to prove you have found all possible solutions.]

Exhaustion

Find the positive integer solutions of the equation (1+1/a)(1+1/b)(1+1/c) = 2

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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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