Page 291 - Math Smart - 7

CHAPTER 13.1 In this chapter

Pupils should be able to:
• recognise the
Ratio relationship between
ratio and proportion
^
13.1.1 Writing ratio • use ratio notation
• simplify ratios
• divide a quantity into
A ratio compares quantities of the same kind or of the same unit. The quantities
two parts in a given ratio
may be numbers, measurements or sums of money. The ratio of one quantity to
another quantity tells us how much the first quantity is as compared to the second
quantity. Ratios can also be used to compare more than two quantities.

There are 2 oranges and 3 pears. We can express the ratio of the number of
oranges to the number of pears in two ways:
The colon (:) in a ratio
• Number of oranges: Number of pears = 2:3
means 'is to'.
• Number of oranges _ 2
Number of pears " Hi 4 : 3 is read as
3
"4 is to 3".
OOO
There are 5 nuts and 3 bolts. ' mrnt m I
OO
The ratio of the number of nuts to the number of bolts = 5:3
The order in which
_ 5
" the ratio is written is
3
The ratio of the number of bolts to the number of nuts = 3:5 important.
.
3
"
5
^ RECALL

O Ruby uses 3 parts flour and 2 parts egg to make pasta,
a) Complete the table.
Amount of
2 6
eggs used
Amount of
3 6 12
flour used
b) The ratio of the amount of flour used to the amount of egg used is
c) The amount of eggs used is j=j of the amount of flour used.

d) The amount of flour used is I times as much as the amount of eggs used.

a) The ratio of the number of ants to the number of butterflies is

b) The ratio of the number of butterflies to the number of ants is