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Days and Dates

Investigate how you can work out what day of the week your birthday will be on next year, and the year after...

Summing Consecutive Numbers

15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?

Always the Same

Arrange the numbers 1 to 16 into a 4 by 4 array. Choose a number. Cross out the numbers on the same row and column. Repeat this process. Add up you four numbers. Why do they always add up to 34?

Your Number Is...

Age 7 to 14 Challenge Level:

Press the button in the interactivity below, and see what happens:

Now try again starting with a different number.

Try again.

Try starting with a fraction... or decimal... or negative number...

Why are your answers ALWAYS the same?


Can you design instructions for similar "Think of a number" machines of your own?
Test them on a partner to check that they lead to your anticipated solutions.
 
 
You may want to take a look at Your Number Was... for a suitable follow-up activity.   

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