smc-680-50-Similarity

Geometry, NAP-L4-CA37

Select the pair of similar triangles.

The triangles are not drawn to scale.

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`text(Triangle 1 and 4)`

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`text(Similar triangles are equiangular.)`

`text(Calculate triangle angles of each option.)`

`text(Triangle 1: 55, 55, 70)`

`text(Triangle 2: 55, 65, 60)`

`text(Triangle 3: 50, 65, 65)`

`text(Triangle 4: 55, 55, 70)`

`:.\ text(Similar triangles have angles: 55, 55, 70)`

Two circles have the same centre, `O`, as shown in the diagram below.

The radius of the small circle is `2/3` the radius of the large circle.

Arc `CD` is 21 cm and the angle between the lines `AC` and `BD` is 45°.

What is the length of the arc `RS` in centimetres?

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`text(42 cm)`

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