1. RATIOS and PROPORTIONS
Cain
Sep 2008

2. RATIO All fractions are ratios!
a comparison of two numbers by division
RATIO
All fractions are ratios!

3. PERCENTS are RATIOS fractions The percent sign (%) means hundredth
One percent is one hundredth
12% is twelve hundredths
75% is 75 out of 100

4. PROPORTIONS A proportion is an equation in the form Vocab
stating that two ratios are equal.
Vocab
a comparison of two numbers by division

5. 7 out of 20 is proportional to what # out of 1000? Write as a fraction
A proportion is an equation in the form
stating that two ratios are equal.
In your notes, write each proportion like this….
7 out of is proportional
to what # out of 1000?
Write as a fraction
Then Solve!

6. = % 100 Proportion is_ of What percent of 400 is 50?
% 100 =
Proportion
Cross Multiply to Solve

7. What % of 400 is 50?
is_ of =
% 100
12.5%
then SOLVE

8. What % of 275 is 33?
CROSS
MULTIPLY

9. Let’s try a different question
17 is 25% of what number?
(let’s use n)
% 100 =
is_ of
17_ n =

10. 17 is 25% of what number?

11. = 13 100 Here’s another one n_ 200 How much is 13% of 200?
(let’s use n) n_ =

12. How much is 13% of 200?

13. = = % 100 % 100 Write in your journal out of means division is_ of
% 100 =
is_ of OR
% 100 =
part_ total

14. Now, using your journal notes, solve the following proportions
Please write down the problem, then solve.
Now, using your journal notes, solve the following proportions
28 is 70% of what number?
n=40
Proportion:
How much is 35% of $20?
n=$7
Proportion:

15. % 100 =
part_ total
What’s part out of total mean?
Brock got 28 out of 40 problems correct on the test. What percent correct did he make?

16. Did you know maps use ratios and proportions?
When a map’s scale is 1 inch to 25 miles, it means every inch on the map represents 25 miles
Represented by 1:25
If on this map, a railway was 6 inches long, how long is it really? (in miles)
The colon means proportion
150 miles
How did you get 150 miles?

17. Ratios & Proportions on Maps
On a map with a scale of 1:25,
a railway was 6 inches long,
how long is it in miles?
this ratio as a fraction is
one (1) inch to 25 (miles)
1:25
is how many miles?

18. Label Your Proportions!
The proportion is
Label Your Proportions!
Cross multiply and the answer is 150 miles

19. Label Your Proportions!
Mrs. Cain’s car uses 9 gallons to travel 180 miles. How much gas is needed for 750 miles?
37.5 gallons
Mike can tile 15 units of a flooring in 2.5 hours. How many units can he tile in 8 hours?
48 units