Page 297 - Math Smart - 7

CHAPTER 13.2 In this chapter

Pupils should be able to:
Proportion • use direct proportion in
context
• solve simple problems
involving ratio and direct
proportion
^ RECALL

To make some bread dough, Mrs Tham uses 3 parts water and 5 parts flour,
a) Complete the table.
Think and Share
Amount of water used 3 9
Amount of flour used 5 10 20 To bake some cakes, a baker
used 40 g of strawberries for
b) The ratio of the amount of water used to the amount of flour used is every 220 g of flour.

c) The amount of flour used Is of the amount of water used.

d) How many mlllilitres of water is used in 3600 g of bread dough? ml

a) The proportion of
strawberries used
13.2.1 Proportion as port of a whole was of the total
amount of strawberries
and flour used.
Proportion is a comparison of the quantity of a part to the quantity of a whole.
b) If the total amount of
A bookstore sells pens in packs of four. There is 1 red pen and 3 blue pens in each strawberries and flour
pack.
that the baker used
was 1040 g, what was
the amount of flour the
baker used?
If the baker used 440 g
of flour to bake 1 cake,
how many such cakes
We can compare the number of red pens to the total number of pens in the
bookstore using ratio. can he bake with 1760 g
of flour?
red pens blue pens

The ratio of the number of red pens to the total number of pens is 1 : 4.
Since 1 in every 4 pens is a red pen, we say that the proportion of red pens is
i of the total number of pens.
We can say that 1 of
of
The ratio of the number of blue pens to the total number of pens is 3 : 4. the pens are red and |
the pens are blue.
of
Since 3 in every 4 pens are blue pens, the proportion of blue pens is |
total
the
number of pens.