Translations and dilations
Translate shapes using vectors and dilate shapes from the origin using a scale factor.
Worked examples
Translating a point using a vector
Straightforward
Problem
Translate point by the vector and state the coordinates of .
1
Add the horizontal component of the vector to the -coordinate.
2
Add the vertical component of the vector to the -coordinate.
3
Write the coordinates of the image.
Answer
Dilating a point from the origin
Moderate
Problem
Point is dilated from the origin by scale factor . State the coordinates of .
1
Write the dilation rule: multiply each coordinate by the scale factor .
where
2
Multiply the -coordinate by .
3
Multiply the -coordinate by .
4
Write the coordinates of the image.
Answer
Finding the scale factor and classifying a dilation
Challenging
Problem
Point is mapped to by a dilation from the origin. Find the scale factor and classify the transformation as an enlargement, reduction or congruent.
1
Find the scale factor by dividing an image coordinate by the corresponding original coordinate.
2
Verify using the -coordinates.
✓
3
Classify the dilation: since , the image is smaller than the original.
, so this is a reduction.
Answer
Scale factor ; the transformation is a reduction.
Practise
Q1·Straightforward
Point is translated by the vector . State the coordinates of .
Explanation
Add each component of the vector to the matching coordinate: and . So .
Q2·Straightforward
Point is translated by the vector . State the coordinates of .
Explanation
and . So .
Q3·Straightforward
Point is translated by the vector . State the coordinates of .
Explanation
and . So .
Q4·Straightforward
A rectangle has vertex . It is translated by the vector . State the coordinates of .
Explanation
and . So .
Q5·Moderate
Point is dilated from the origin by scale factor . State the coordinates of .
Explanation
A dilation from the origin by scale factor maps . With : and . So .
Q6·Moderate
Point is dilated from the origin by scale factor . State the coordinates of .
Explanation
and . So .
Q7·Moderate
Triangle has vertex . It is dilated from the origin by scale factor . State the coordinates of .
Explanation
and . So .
Q8·Moderate
Point is dilated from the origin by scale factor . State the coordinates of .
Explanation
and . So .
Q9·Challenging
Point is mapped to by a dilation from the origin. What is the scale factor?
Explanation
Scale factor . Check: ✓. The scale factor is .
Q10·Challenging
Point is mapped to by a dilation from the origin. What is the scale factor?
/
Explanation
Scale factor . Check: ✓. The scale factor is .
Q11·Challenging
Point is mapped to by a dilation from the origin. What is the scale factor?
/
Explanation
Scale factor . Check: ✓. The scale factor is .
Q12·Challenging
Triangle has side lengths cm, cm and cm. It is mapped to triangle with side lengths cm, cm and cm. Classify this transformation.
Explanation
The scale factor is . Since , the image is larger than the original, so the transformation is an enlargement.