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Percentage Unchanged

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Digit Sum

What is the sum of all the digits in all the integers from one to one million?

The Power of $x$

Age 14 to 16 Short
Challenge Level

Find the value of $x$, where $$2^{x+1}-2^{x-1}=12$$


This problem is adapted from the World Mathematics Championships
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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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