Reasoning, convincing and proving

There are 514 NRICH Mathematical resources connected to Reasoning, convincing and proving
Thousand Words
problem

Thousand words

Age
16 to 18
Challenge level
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Here the diagram says it all. Can you find the diagram?
Honey Bees
problem

Honey bees

Age
14 to 16
Challenge level
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How many bees could fly 1000 miles if they had 10 gallons of honey?
Prime sequences
problem

Prime sequences

Age
16 to 18
Challenge level
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This group tasks allows you to search for arithmetic progressions in the prime numbers. How many of the challenges will you discover for yourself?
Weekly Lies
problem

Weekly lies

Age
11 to 14
Challenge level
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Mr Ross tells truths or lies depending on the day of the week. Can you catch him out?
Online
game

Online

A game for 2 players that can be played online. Players take it in turns to select a word from the 9 words given. The aim is to select all the occurrences of the same letter.
Without Calculus
problem

Without calculus

Age
16 to 18
Challenge level
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Given that u>0 and v>0 find the smallest possible value of 1/u + 1/v given that u + v = 5 by different methods.
Big, Bigger, Biggest
problem

Big, bigger, biggest

Age
16 to 18
Challenge level
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Which is the biggest and which the smallest of $2000^{2002}, 2001^{2001} \text{and } 2002^{2000}$?
Winning Team
problem

Winning team

Age
11 to 14
Challenge level
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Nine cross country runners compete in a team competition in which there are three matches. If you were a judge how would you decide who would win?
Cyclic Quad Jigsaw
problem

Cyclic quad jigsaw

Age
14 to 16
Challenge level
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A picture is made by joining five small quadrilaterals together to make a large quadrilateral. Is it possible to draw a similar picture if all the small quadrilaterals are cyclic?
Pent
problem

Pent

Age
14 to 18
Challenge level
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The diagram shows a regular pentagon with sides of unit length. Find all the angles in the diagram. Prove that the quadrilateral shown in red is a rhombus.