2. A ratio is a comparison of two quantities.
Write a ratio comparing the number of squares to
the number of circles.
3 to 2
3:2
3
2
3. Two equal ratios form a proportion.
Circles 2 4
squares 3 6
2=4
3 6
proportion
4. Solving proportions
x3
3= n n=9 Look for a multiplier
4 12 (scale factor)
x3
30 7n
No obvious multiplier -
5= n
Cross multiply
7 6 7n = 30
7 7
2
n=47
5.
6. Three out of every 10 adults segregate their food.
a) Write this information as a ratio.
Segregators 3
total 10
b) In a group of 90 people, how many would you
expect to be food segregators?
x9
Segregators 3 = x
x = 27
total 10 90
x9
7. The scale on a map is 1 inch = 20 miles.
a) If two towns are 4 ½ inches apart on the map, how
many miles apart are they?
1x 20 · 4 ½
x = 20 · 9 = 180 = 90
Inch 1 = 4½ 2 2
Mile 20 x 90 miles apart
b) If two towns are 75 miles apart, how far apart will
they be on the map?
75 20x 20x = 75 3 ¾ inches apart
Inch 1 = x 20 20
Mile 20 75 x = 75 5 = 15
20 5 4
11. Decimals Percents Move decimal point
two places right
37
0.37 = 37%
100
0.0004 = 0.04%
36.7 = 3670%
12. The Percent Proportion
percent part
=
100 whole
What is 20% of 18?
20 x 100x = 360
= 100 100
100 18
x = 3.6
13. 3 is 6% of what number?
part percent whole
percent part
=
100 whole
6 3
=
100 x
6x = 300
6 6
x = 50
14. A dress that normally sells for $80 is on sale for $52.
What is the “percent off”?
1) Find the markdown
80 – 52 = 28
2) Percent: x Part: 28 Whole: 80
x 28
=
100 80
80x = 2800
x = 35
35 % off
