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Black and White Socks

Age 14 to 16 Short Challenge Level:


There are 20 black socks and $n$ white socks in a drawer.

When a sock is taken from the drawer, the probability that it is white is $\dfrac{1}{n}$.

What is the value of $n$?



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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