Similarity and congruence

There are 62 NRICH Mathematical resources connected to Similarity and congruence
Wedge on Wedge
problem

Wedge on wedge

Age
14 to 16
Challenge level
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Two right-angled triangles are connected together as part of a structure. An object is dropped from the top of the green triangle where does it pass the base of the blue triangle?
How big?
problem

How big?

Age
11 to 14
Challenge level
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If the sides of the triangle in the diagram are 3, 4 and 5, what is the area of the shaded square?
Flower
problem

Flower

Age
16 to 18
Challenge level
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Six circles around a central circle make a flower. Watch the flower as you change the radii in this circle packing. Prove that with the given ratios of the radii the petals touch and fit perfectly.
All Tied Up
problem

All tied up

Age
14 to 16
Challenge level
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A ribbon runs around a box so that it makes a complete loop with two parallel pieces of ribbon on the top. How long will the ribbon be?
Number the Sides
problem

Number the sides

Age
7 to 11
Challenge level
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The triangles in these sets are similar - can you work out the lengths of the sides which have question marks?
Bus Stop
problem

Bus stop

Age
14 to 16
Challenge level
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Two buses leave at the same time from two towns Shipton and Veston on the same long road, travelling towards each other. At each mile along the road are milestones. The buses' speeds are constant and in the ratio 5 to 4. The buses travel to and fro between the towns. What milestones are at Shipton and Veston?
Two Right Angles
problem

Two right angles

Age
14 to 16
Challenge level
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Weekly Problem 4 - 2008
In the figure given in the problem, calculate the length of an edge.
Folding Squares
problem

Folding squares

Age
14 to 16
Challenge level
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The diagonal of a square intersects the line joining one of the unused corners to the midpoint of the opposite side. What do you notice about the line segments produced?
Slippage
problem

Slippage

Age
14 to 16
Challenge level
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A ladder 3m long rests against a wall with one end a short distance from its base. Between the wall and the base of a ladder is a garden storage box 1m tall and 1m high. What is the maximum distance up the wall which the ladder can reach?
Another Triangle in a Triangle
problem

Another triangle in a triangle

Age
16 to 18
Challenge level
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Can you work out the fraction of the original triangle that is covered by the green triangle?