Calculating scale factors

1 Completethesentences.

ShapeBisanenlargement,byascalefactorof ,ofshapeA.

ShapeCisanenlargement,byascalefactorof ,ofshapeA.

ShapeDisanenlargement,byascalefactorof ,ofshapeA.

2 ShapeBisanenlargementofshapeA.ShapeCisnotan

enlargementofshapeA.

Talktoapartneraboutwhythisisthecase.

3 TickalltheshapesthatareanenlargementofshapeA.

Howdoyouknowwhichshapesareenlargements?

4 Thetwotrianglesaresimilar.

Findthelengthofa.

7cm

5cm

a= cm

©WhiteRoseMaths2019

A

B

C

D

A

B

C

a

15cm

A

D

B

C

5 Thetwotrianglesaresimilar.

Findtheareaofthesmallertriangle.

area= cm2

6 Thesetwochildren’stoysaresimilar.

Findthelengthmarkedy.

y= cm2

©WhiteRoseMaths2019

7 Therectangleisenlargedbyascalefactor.

Theperimeteroftheenlarged

rectangleis64m.

Whatisthescalefactorofenlargement?

scalefactor=

8 Thediagramshowsthreesimilartriangles.

Calculatethemissingvalues.

a

b

c

d

6mm 18mm 27mm

21mm

37°

53°

a= b= c= d=

4cm 24cm

30cm

18cm y

20cm

5cm

2.8m

5.2m