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problem

Crystal symmetry

16 to 18

Use vectors and matrices to explore the symmetries of crystals.

problem

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2009 challenge

11 to 18

We asked what was the most interesting fact that you can find out about the number 2009. See the solutions that were submitted.

problem

What salt?

16 to 18

Can you deduce why common salt isn't NaCl_2?

problem

Perfect eclipse

14 to 16

Use trigonometry to determine whether solar eclipses on earth can be perfect.

problem

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Our numbers

5 to 7

These spinners will give you the tens and unit digits of a number. Can you choose sets of numbers to collect so that you spin six numbers belonging to your sets in as few spins as possible?

problem

Robert's spreadsheet

14 to 16

Robert noticed some interesting patterns when he highlighted square numbers in a spreadsheet. Can you prove that the patterns will continue?

problem

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Data shapes

5 to 7

Sara and Will were sorting some pictures of shapes on cards. "I'll collect the circles," said Sara. "I'll take the red ones," answered Will. Can you see any cards they would both want?