Difference between revisions of "1967 IMO Problems/Problem 6"

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In a sports contest, there were m medals awarded on n successive days (n >
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In a sports contest, there were <math>m</math> medals awarded on <math>n</math> successive days <math>(n >
1). On the first day, one medal and 1/7 of the remaining m - 1 medals
+
1)</math>. On the first day, one medal and <math>\frac{1}{7}</math> of the remaining <math>m - 1</math> medals
were awarded. On the second day, two medals and 1/7 of the now remaining
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were awarded. On the second day, two medals and <math>\frac{1}{7}</math> of the now remaining
medals were awarded; and so on. On the n-th and last day, the remaining n
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medals were awarded; and so on. On the n-th and last day, the remaining <math>n</math>
 
medals were awarded. How many days did the contest last, and how many
 
medals were awarded. How many days did the contest last, and how many
 
medals were awarded altogether?
 
medals were awarded altogether?
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 +
==Solution==
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This is not a particularly elegant solution, but if you start from 1 and go all the way in a clever method, by only guessing those that are 1 more than a multiple of 7, you arrive at the answer of 36.
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== See Also == {{IMO box|year=1967|num-b=5|after=Last Question}}

Latest revision as of 10:02, 3 June 2021

In a sports contest, there were $m$ medals awarded on $n$ successive days $(n > 1)$. On the first day, one medal and $\frac{1}{7}$ of the remaining $m - 1$ medals were awarded. On the second day, two medals and $\frac{1}{7}$ of the now remaining medals were awarded; and so on. On the n-th and last day, the remaining $n$ medals were awarded. How many days did the contest last, and how many medals were awarded altogether?

Solution

This is not a particularly elegant solution, but if you start from 1 and go all the way in a clever method, by only guessing those that are 1 more than a multiple of 7, you arrive at the answer of 36.

See Also

1967 IMO (Problems) • Resources
Preceded by
Problem 5
1 2 3 4 5 6 Followed by
Last Question
All IMO Problems and Solutions