NRICH: Your Number Was...

Think of a number and follow my instructions. Tell me your answer, and I’ll tell you what you started with! Can you explain how I know?

This problem follows on from Your Number Is…

Press the button in the interactivity to investigate what this machine does.

Try starting with other numbers – maybe decimals or negative numbers.

How is the machine working out your starting numbers?

Can you devise your own set of instructions so you can work out someone else’s starting numbers in the same way?

Age 11 to 14


Algebra & Pre-Algebra, Equations
Middle School, High School, Educator

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NRICH (University of Cambridge)

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Challenge
Online Interactive Activity

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