Reasoning, convincing and proving

There are 514 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?
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?
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?
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.
Particularly general
problem

Particularly general

Age
16 to 18
Challenge level
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By proving these particular identities, prove the existence of general cases.
Advent Calendar 2011 - Secondary
problem

Advent calendar 2011 - secondary

Age
11 to 18
Challenge level
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Advent Calendar 2011 - a mathematical activity for each day during the run-up to Christmas.
Calculating with cosines
problem

Calculating with cosines

Age
14 to 18
Challenge level
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If I tell you two sides of a right-angled triangle, you can easily work out the third. But what if the angle between the two sides is not a right angle?