Reasoning, convincing and proving

There are 458 NRICH Mathematical resources connected to Reasoning, convincing and proving
Staircase
problem

Staircase

Age
16 to 18
Challenge level
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Solving the equation x^3 = 3 is easy but what about solving equations with a 'staircase' of powers?
Tetra Inequalities
problem

Tetra Inequalities

Age
16 to 18
Challenge level
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Can you prove that in every tetrahedron there is a vertex where the three edges meeting at that vertex have lengths which could be the sides of a triangle?
Diverging
problem

Diverging

Age
16 to 18
Challenge level
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Show that for natural numbers x and y if x/y > 1 then x/y>(x+1)/(y+1}>1. Hence prove that the product for i=1 to n of [(2i)/(2i-1)] tends to infinity as n tends to infinity.
Latin Numbers
problem

Latin Numbers

Age
14 to 16
Challenge level
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Can you create a Latin Square from multiples of a six digit number?
Pair Squares
problem

Pair Squares

Age
16 to 18
Challenge level
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The sum of any two of the numbers 2, 34 and 47 is a perfect square. Choose three square numbers and find sets of three integers with this property. Generalise to four integers.
Basic Rhythms
problem

Basic Rhythms

Age
16 to 18
Challenge level
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Explore a number pattern which has the same symmetries in different bases.
Target Six
problem

Target Six

Age
16 to 18
Challenge level
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Show that x = 1 is a solution of the equation x^(3/2) - 8x^(-3/2) = 7 and find all other solutions.
Binary Squares
problem

Binary Squares

Age
16 to 18
Challenge level
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If a number N is expressed in binary by using only 'ones,' what can you say about its square (in binary)?
Prime AP
problem

Prime AP

Age
16 to 18
Challenge level
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What can you say about the common difference of an AP where every term is prime?
Sixational
problem

Sixational

Age
14 to 18
Challenge level
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The nth term of a sequence is given by the formula n^3 + 11n. Find the first four terms of the sequence given by this formula and the first term of the sequence which is bigger than one million. Prove that all terms of the sequence are divisible by 6.