1. 8.2 Inverse and Joint Variation.notebook March 19, 2013
Inverse Variation x y k
rate time distance
20 3 60
30 2 60
40 1.5
50 1.2
60 1
xy = k
k ­ constant

2. 8.2 Inverse and Joint Variation.notebook March 19, 2013
If y is inversely proportional to x and y = 6 when x = 5, find x when y = 12.

3. 8.2 Inverse and Joint Variation.notebook March 19, 2013
Jointly proportional ­ more than 2 variables.
jointly ­ direct inverse
If z varies jointly as x and the square root of y, and z = 6 when x =3 and y = 16,
find z when x = 7 and y = 4.

4. 8.2 Inverse and Joint Variation.notebook March 19, 2013
The electrical resistance of a wire varies directly as its length and inversely as the square
of its diameter. One hundred meters of a wire with diameter 6mm has resistance 12 ohms.
Eighty meters of a second wire has resistance 15 ohms. Find the diameter of the second wire.