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The Best Card Trick?

Age 11 to 16
Challenge Level Yellow star
  • Problem
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James, from Hampton School, gave us his ideas on how to order the cards to show to his partner:

For the first set of 5 cards, the two cards with the same suit are the diamonds: the 4d should be the "base" card as the gap between the 4d and the 6d is 2, which can be expressed using the remaining three cards with l h m. Therefore, from right to left, the cards would be the 4 of diamonds followed by the 5 of clubs, the 10 of spades and the 9 of hearts, allowing you to guess the 6 of diamonds.

Jamie and Monty from Hurstpierpoint Prep School came to the same conclusion.

Aswaath, from Garden International School, Kuala Lumpur, sent us his thoughts on how he would show his partner the cards:

For the first set of cards, I would place four cards in this particular order: 4d, 5c, 10s and 9h. I would keep 6d the secret card.

For the second set of cards, I would place four cards in this particular order: Qh, 8d, 10s and 2c. I would keep 3h the secret card.

For the third set of cards, I would place four cards in this particular order: 7h, 7s, 7d and 7c. I would keep Kh the secret card.

Great - you all seem to have understood Charlie's crib sheet well!

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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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