Flashcards · Maths · Transformations and Similarity
Enlargements
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What is an enlargement?
A transformation that changes the size of a shape and keeps its angles.
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What is the scale factor?
The number by which every length is multiplied.
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What is the centre of enlargement?
The fixed point from which the distances are scaled.
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What happens to the angles in an enlargement?
They stay the same.
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What is the scale factor if a side grows from 4 cm to 10 cm?
\(\dfrac{10}{4} = 2.5\).
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What does a scale factor of \(\dfrac{1}{2}\) do to a shape?
It halves every length, giving a smaller shape.
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How do you find the image of a point?
Multiply its distance from the centre by the scale factor, in the same direction.
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How do you find the centre of an enlargement?
Draw lines through each corner and its image and find where they meet.
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What do you give to describe an enlargement fully?
The scale factor and the centre of enlargement.
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Is an enlarged shape congruent to the original?
No, unless the scale factor is 1.
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Is an enlarged shape similar to the original?
Yes, the shapes are similar.
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What is the image of \((2, 3)\) for scale factor 3 and centre the origin?
\((6, 9)\).
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What does a negative scale factor do?
It puts the image on the opposite side of the centre (Higher tier).
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Which transformation is an enlargement with scale factor \(-1\)?
A rotation of \(180^\circ\) about the centre (Higher tier).
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How do you work out the scale factor from a side?
Image length divided by object length.
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What are corresponding sides?
Sides in the same position on the object and the image.