Creating and manipulating expressions and formulae

There are 198 NRICH Mathematical resources connected to Creating and manipulating expressions and formulae
AMGM
problem

AMGM

Age
14 to 16
Challenge level
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Can you use the diagram to prove the AM-GM inequality?
Hot Pursuit
problem

Hot Pursuit

Age
11 to 14
Challenge level
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I added together the first 'n' positive integers and found that my answer was a 3 digit number in which all the digits were the same...
Look before you leap
problem

Look before you leap

Age
16 to 18
Challenge level
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Relate these algebraic expressions to geometrical diagrams.
Around and Back
problem

Around and Back

Age
14 to 16
Challenge level
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A cyclist and a runner start off simultaneously around a race track each going at a constant speed. The cyclist goes all the way around and then catches up with the runner. He then instantly turns around and heads back to the starting point where he meets the runner who is just finishing his first circuit. Find the ratio of their speeds.
Adding in Rows
problem

Adding in Rows

Age
11 to 14
Challenge level
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List any 3 numbers. It is always possible to find a subset of adjacent numbers that add up to a multiple of 3. Can you explain why and prove it?
Little and Large
problem

Little and Large

Age
16 to 18
Challenge level
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A point moves around inside a rectangle. What are the least and the greatest values of the sum of the squares of the distances from the vertices?
Why 24?
problem

Why 24?

Age
14 to 16
Challenge level
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Take any prime number greater than 3 , square it and subtract one. Working on the building blocks will help you to explain what is special about your results.
What's Possible?
problem

What's Possible?

Age
14 to 16
Challenge level
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Many numbers can be expressed as the difference of two perfect squares. What do you notice about the numbers you CANNOT make?
Quick Times
problem

Quick Times

Age
11 to 14
Challenge level
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32 x 38 = 30 x 40 + 2 x 8; 34 x 36 = 30 x 40 + 4 x 6; 56 x 54 = 50 x 60 + 6 x 4; 73 x 77 = 70 x 80 + 3 x 7 Verify and generalise if possible.
Fair Shares?
problem

Fair Shares?

Age
14 to 16
Challenge level
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A mother wants to share a sum of money by giving each of her children in turn a lump sum plus a fraction of the remainder. How can she do this in order to share the money out equally?