Units Of Measurement And Applications Worksheet Page 29
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44WORKED EXAMPLE 4
The ratio of the number of boys to girls in a school is 7 : 6.
If there are 354 girls in the school, how many boys are there?
Solve
Think
Apply
boys : girls = 7 : 6
boys
Using fraction notation, write
7 __
____
=
boys : 354 = 7 : 6
354
6
two equivalent ratios. Treat
boys
7 __
7 __
____
∴ boys =
× 354
this as an equation and solve.
=
Using fraction notation
6
354
6
= 413
(Remember the order of terms is important!)
Treat this as an equation. Solve by multiplying
There are 413 boys.
both sides by 354.
boys
7 __
____
× 354
=
× 354
354
6
7 __
∴ boys =
× 354 = 413
6
7
The ratio of the number of boys to girls in a school is 9 : 8 and there are 312 girls at the school. Complete the
following to fi nd the number of boys.
boys
____
9 _
=
□
8
9 _
∴ boys =
× ____ = ____
8
8
At an electrical store the ratio of profi t to sales is 2 : 7. If the annual sales for the year were $145 600, what was
the annual profi t?
9
The ratio of Ben’s net salary to the tax he pays is 10 : 3. Find his net salary if he paid $14 580 in tax for 1 year.
WORKED EXAMPLE 5
The ratio of boys to girls in a school is 8 : 7.
If there are 264 boys in the school, how many girls are there?
Solve
Think
Apply
boys : girls = 8 : 7
Using fraction notation, write
264
8 __
____
=
girls : boys = 7 : 8
girls
7
two equivalent ratios. Change
girls
7 __
girls
____
=
the order so that the unknown
7 __
____
Using fraction notation
=
264
8
264
8
is the fi rst term of the ratio.
Treat this as an equation and solve by
7 __
∴ girls =
× 264
Treat this as an equation and
8
multiplying both sides by 264.
solve.
= 231
girls
7 __
____
×
=
×
264
264
264
8
There are 231 girls.
7 __
∴ girls =
× 264 = 231
8
10
The ratio of males to females at a basketball match is 10 : 9. If there are 470 males at the match, complete the
following to fi nd the number of females.
□
females
_______
_______
10
9 __
=
__
=
so
□
9
10
females
9 __
∴ females =
× ____ = ____
10
Chapter 2
Units of measurement and applications
63
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