Similarity and congruence

There are 62 NRICH Mathematical resources connected to Similarity and congruence
Pythagoras Proofs
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Pythagoras proofs

Age
11 to 16
Challenge level
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Can you make sense of these three proofs of Pythagoras' Theorem?

Triangle in a Trapezium
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Triangle in a trapezium

Age
11 to 16
Challenge level
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Can you find and prove the relationship between the area of a trapezium and the area of a triangle constructed within it?
The square under the hypotenuse
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The square under the hypotenuse

Age
14 to 16
Challenge level
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Can you work out the side length of a square that just touches the hypotenuse of a right angled triangle?
Kite in a Square
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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?
Two Trees
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Two trees

Age
16 to 18
Challenge level
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Two trees 20 metres and 30 metres long, lean across a passageway between two vertical walls. They cross at a point 8 metres above the ground. What is the distance between the foot of the trees?
Figure of Eight
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Figure of eight

Age
14 to 16
Challenge level
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On a nine-point pegboard a band is stretched over 4 pegs in a "figure of 8" arrangement. How many different "figure of 8" arrangements can be made ?
Triangle in a Triangle
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Triangle in a triangle

Age
14 to 16
Challenge level
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Can you work out the fraction of the original triangle that is covered by the inner triangle?
Fit for photocopying
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Fit for photocopying

Age
14 to 16
Challenge level
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Explore the relationships between different paper sizes.
Triangle midpoints
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Triangle midpoints

Age
14 to 16
Challenge level
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You are only given the three midpoints of the sides of a triangle. How can you construct the original triangle?

Trapezium Four
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Trapezium four

Age
14 to 16
Challenge level
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The diagonals of a trapezium divide it into four parts. Can you create a trapezium where three of those parts are equal in area?