![Mini Cross-Number](/sites/default/files/styles/medium/public/thumbnails/content-id-10143-icon.png?itok=zUwMU-MB)
Reasoning, convincing and proving
![Mini Cross-Number](/sites/default/files/styles/medium/public/thumbnails/content-id-10143-icon.png?itok=zUwMU-MB)
![The London Eye](/sites/default/files/styles/medium/public/thumbnails/content-id-10114-icon.png?itok=m5iQZtzi)
problem
The London Eye
The 80 spokes of The London Eye are made from 4 miles of cable. What is the approximate circumference of the wheel?
![Would you like a Jelly Baby?](/sites/default/files/styles/medium/public/thumbnails/content-id-10105-icon.png?itok=grUUd5C7)
problem
Would you like a Jelly Baby?
What is the smallest number of jelly babies Tom must take, to be certain that he gets at least one of each flavour?
![Strange Bank Account](/sites/default/files/styles/medium/public/thumbnails/content-id-9923-icon.jpg?itok=z5kDCAKZ)
problem
Strange Bank Account
Imagine a very strange bank account where you are only allowed to do two things...
![Magical Products](/sites/default/files/styles/medium/public/thumbnails/content-id-7189-icon.png?itok=jwR44kGZ)
problem
Magical Products
Can you place the nine cards onto a 3x3 grid such that every row, column and diagonal has a product of 1?
![Placeholder: several colourful numbers](/themes/nrich/images/nrich_small_placeholder.png)
article
Binomial Coefficients
An introduction to the binomial coefficient, and exploration of some of the formulae it satisfies.
![To Run or not to Run?](/sites/default/files/styles/medium/public/thumbnails/content-04-weekly-prob3-icon.png?itok=54EvscOs)
problem
To Run or not to Run?
If an athlete takes 10 minutes longer to walk, run and cycle three miles than he does to cycle all three miles, how long does it take him?
![Summing geometric progressions](/sites/default/files/styles/medium/public/thumbnails/content-id-8054-icon.png?itok=rh-dBjXB)
problem
Summing geometric progressions
Watch the video to see how to sum the sequence. Can you adapt the method to sum other sequences?
![Kite in a Square](/sites/default/files/styles/medium/public/thumbnails/content-id-8301-icon.png?itok=k5PyV7gm)
problem
Kite in a Square
Can you make sense of the three methods to work out what fraction of the total area is shaded?
![Interpolating polynomials](/sites/default/files/styles/medium/public/thumbnails/content-id-7670-icon.png?itok=C5rfJW86)
problem
Interpolating polynomials
Given a set of points (x,y) with distinct x values, find a polynomial that goes through all of them, then prove some results about the existence and uniqueness of these polynomials.