Similar figures

Question 1

When is a figure said to be similar?

Answer 1

SIMILARITY
Two figures are said to be similar if they
are basically the same shape, with one being
an enlargement or a reduction of the other.
The two similar shapes will have :-
• their corresponding angles equal
• their corresponding sides in the same ratio
(the same scale factor)

Question 2

When is a figure said to be congruent?

Answer 2

Two figures are said to be congruent if they
are exactly the same shape and the same size.
i.e. one figure can be lifted and placed
exactly on top of the other.

Question 3

How do we know if triangles are similar?

Answer 3

If pairs of corresponding angles are equal,
=> ratios of corresponding sides are equal.
=> triangles are similar.
If ratio of pairs of corresponding sides are equal,
=> corresponding angles are equal.
=> triangles are similar.

Question 4

How do we calculate similar areas?

Answer 4

The AREA scale factor = the LINEAR scale factor “SQUARED”.

Question 5

How do we calculate similar volumes?

Answer 5

The VOLUME scale factor = the LINEAR scale factor “CUBED”.