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Farey Sequences

There are lots of ideas to explore in these sequences of ordered fractions.

Do Unto Caesar

At the beginning of the night three poker players; Alan, Bernie and Craig had money in the ratios 7 : 6 : 5. At the end of the night the ratio was 6 : 5 : 4. One of them won $1 200. What were the assets of the players at the beginning of the evening?

Plutarch's Boxes

According to Plutarch, the Greeks found all the rectangles with integer sides, whose areas are equal to their perimeters. Can you find them? What rectangular boxes, with integer sides, have their surface areas equal to their volumes?

Bull's Eye

Age 11 to 14 Challenge Level:

The diagram below shows circles with radii 3, 4, 5, 6 and 7 cm.

What fractions of the largest circle are each of the two shaded regions?

5 concentric circles. forming four rings. The innermost ring is shaded pink and the second-largest is shaded green.

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.
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