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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 $S_1, S_2, ... S_{r-1}$.
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 $\sqrt{2}$?
Age 16 to 18
Challenge Level
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.
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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NRICH is part of the family of activities in the Millennium Mathematics Project.
NRICH is part of the family of activities in the Millennium Mathematics Project.