You may also like
Always Two
Find all the triples of numbers a, b, c such that each one of them plus the product of the other two is always 2.
Not Continued Fractions
Which rational numbers cannot be written in the form x + 1/(y + 1/z) where x, y and z are integers?
Surds
Find the exact values of x, y and a satisfying the following system of equations: 1/(a+1) = a - 1 x + y = 2a x = ay
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.
Copyright © 1997 - 2021. University of Cambridge.
All rights reserved.
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.