Page 236 - SK Year 5 Mathematics DLP

SOLVE THE PROBLEMS

1 Zariq designed an ornamental fish pond by
composing two shapes. He will build a fence 1 m 8 m 1 m
around the pond. What is the length of the fence?

20 m

Understand the problem
• The composition of a rectangle and regular octagon.
• The pond measurements as in the plan. 10 m

• Find the length of the fence around the pond.

Plan the strategy the length
of the outer
• Mark the length of the outer sides of the pond. sides of the
• Add the length of all outer sides to find the 8 m pond
length of the fence.

20 m
Solve

The length of the fence 10 m
= length of the outer sides + length of the outer sides of
of the rectangular pond the regular octagon pond
= (1 m + 20 m + 10 m + 20 m + 1 m) + (7 × 8 m)
= 52 m + 56 m
= 108 m

Check
Perimeter of the pond
Perimeter of the pond = (2 × 20 m) + (2 × 10 m)
= 8 × 8 m = 40 m + 20 m

= 64 m = 60 m
The perimeter of the outer sides of the pond = 64 m + 60 m − (2 × 8 m)
= 124 m − 16 m
= 108 m

The length of the fence is 108 m.

228 • Ask pupils to individually create an object such as a picture frame and
6.5.1 a greeting card using a composition of two regular polygons. Ask them
to measure the perimeter of the object.