Reasoning, convincing and proving

There are 458 NRICH Mathematical resources connected to Reasoning, convincing and proving
Mini Cross-Number
problem

Mini Cross-Number

Age
11 to 14
Challenge level
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Which digit replaces x in this crossnumber?
The London Eye
problem

The London Eye

Age
14 to 16
Challenge level
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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?
problem

Would you like a Jelly Baby?

Age
11 to 14
Challenge level
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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
problem

Strange Bank Account

Age
11 to 14
Challenge level
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Imagine a very strange bank account where you are only allowed to do two things...
Magical Products
problem

Magical Products

Age
11 to 14
Challenge level
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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
article

Binomial Coefficients

An introduction to the binomial coefficient, and exploration of some of the formulae it satisfies.
To Run or not to Run?
problem

To Run or not to Run?

Age
11 to 14
Challenge level
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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
problem

Summing geometric progressions

Age
14 to 18
Challenge level
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Watch the video to see how to sum the sequence. Can you adapt the method to sum other sequences?
Kite in a Square
problem

Kite in a Square

Age
14 to 18
Challenge level
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Can you make sense of the three methods to work out what fraction of the total area is shaded?
Interpolating polynomials
problem

Interpolating polynomials

Age
16 to 18
Challenge level
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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.