## Proportions review

### What is a ratio?

A ratio is teh comparison of the quantity of two properties or items

### What is a proportion?

Proportion is an equation that states that two ratios are equal
for instance a/b = c/d

### How do I convert from one unit to another using proportions?

Make a proportion quation using
The conversion ratio and
The a conversion statement for the unknown
For example To convert 2 feet into inches
make two statements
1 foot =12 inches
2 feet = x
write them as ratios
1 foot/12 inches = 2 feets/x
cross multiply
x = 24 feet

### How to find arc length, curcumference or angle using proportion

x degrees/360 degrees = arc length /circumference
For example:
If the circumference of a circle is 24cm, what is the central angle that subtends an arc AB whose length is 4cm?
x degrees/360 = 4cm/24cm
cross multiply
24 x = 1440
divide both sides by 24
x = 60 degrees

### How to find side length of similar triangles

The scale factor above is n
This means that each side on the smaller triangle is multiplied by n to get the corresponding side length of the larger triangle.
If the side lenght of the base of the small traingle is 4cm, and n is 2.
then
x/2x = 4/a
cross multiply
ax = 8x
a = 8cm

### How to solve problems where two variables x and y are directly proportional

### How to solve problems where the two variable x and y are inversely proportional