Ratios And Rates Worksheet - Chapter 3 Page 30
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38■
Why can you use the equation 8
63
6
to solve for the
E.
number of rock CDs?
What proportion can you use to solve for the number of rap
F.
CDs?
G.
What equation can you use to solve for the number of rap CDs?
H.
Use the equations in parts E and G to calculate the number of
rock CDs and rap CDs they have.
Reflecting
Why should the number of rap CDs be half the number of
I.
rock CDs?
Why might you call the method you used to solve the
J.
proportions “cross-multiplying”? Why does it work?
WORK WITH
the Math
Example 1
Solving part-to-part ratio problems
To make green paint, the paint store mixes yellow and blue paint in the ratio
of 2 : 3. If they used 15 L of yellow paint, how much blue paint did they use?
Aaron’s Solution
To determine the amount of blue paint, I set up a proportion.
2
1
5
=
■
3
■
I can multiply each side of the equation by 1 without changing
2 x
15 x 3
=
■
■
3 x
x 3
the equation. To get a common denominator, I multiplied the
■
■
3
1
3
right side by
and the left side by
.
■
■
1
3
3
■
I knew the numerators were equal since two fractions with the
2 x
= 15 x 3
same denominator are only equal if their numerators are equal.
15
x 3
■
=
I solved by dividing 3
15 by 2.
2
4
5
=
, or 22.5
2
They used 22.5 L of blue paint.
131
Ratios and Rates
NEL
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