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Which is bigger: $9^{10}$ or $10^{9}$?

Now find a way to use your calculator to compare $99^{100}$ and $100^{99}$.

Work out which is bigger out of $999^{1000}$ and $1000^{999}$.



NOTES AND BACKGROUND

This challenge calls for some experimentation with numbers and for some ingenuity in finding a solution. There are several possible methods of solution.

Optional extension challenge: If you solved the above, you might wish to consider which is bigger for the same sort of problem with a billion 9s and a billion 0s.

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Telescoping Series

Find $S_r = 1^r + 2^r + 3^r + ... + n^r$ where r is any fixed positive integer in terms of $S_1, S_2, ... S_{r-1}$.

Growing

Which is larger: (a) 1.000001^{1000000} or 2? (b) 100^{300} or 300! (i.e.factorial 300)

Climbing Powers

$2\wedge 3\wedge 4$ could be $(2^3)^4$ or $2^{(3^4)}$. Does it make any difference? For both definitions, which is bigger: $r\wedge r\wedge r\wedge r\dots$ where the powers of $r$ go on for ever, or $(r^r)^r$, where $r$ is $\sqrt{2}$?

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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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