Geometry - JSS3 Mathematics Past Questions and Answers - page 2

11

Two similar rectangles have lengths in the ratio 2:3. If the area of the smaller rectangle is 36 cm², find the area of the larger rectangle.

Let the scale factor between the rectangles be 

𝑘=3/2

Area of the larger rectangle =𝑘^2× Area of the smaller rectangle

Area of the larger rectangle =(3/2)2×36=

Area of the larger rectangle 

=9/4×36

Area of the larger rectangle 

=81 cm²

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12

Two similar triangles have an area ratio of 9:16. If the smaller triangle has an area of 36 cm², find the area of the larger triangle.

Let the scale factor between the triangles be 

𝑘=16/9=4/3

Area of the larger triangle =𝑘^2 × Area of the smaller triangle

Area of the larger triangle =

(4/3)2×36

Area of the larger triangle =16/9×36

Area of the larger triangle 

=64 cm²

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13

A cube has a volume of 125 cm³. If a similar cube has a side length twice that of the original cube, find the volume of the larger cube.

Let the scale factor between the cubes be 𝑘=2.

Volume of the larger cube =𝑘 ^3 × Volume of the smaller cube

Volume of the larger cube 

=⅔×125

Volume of the larger cube 

=8×125

Volume of the larger cube 

=1000 cm³

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14

Two similar triangles have sides in the ratio 2:3. If the smaller triangle has a height of 8 cm, find the height of the larger triangle.

Let the scale factor between the triangles be 

𝑘=3/2

Height of the larger triangle =𝑘× Height of the smaller triangle

Height of the larger triangle =3/2×8

Height of the larger triangle 

=12 cm

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15

A cylinder has a radius of 4 cm and height of 10 cm. If a similar cylinder has a radius of 6 cm, find its height.

Let the scale factor between the cylinders be 

𝑘=6/4=3/2 .

Height of the larger cylinder =𝑘× Height of the smaller cylinder

Height of the larger cylinder 

=3/2×10

Height of the larger cylinder 

=15 cm

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