Direct proportion?n = the number of cans of coke you buy from a machine.

C = the total cost of the cans.

C is directly proportional to n.

n

C

C = kn

Direct proportion?d = the diameter of a circle.

C = the Circumference of the circle.

C is directly proportional to d.

d

C

C = kd

t

v

Direct proportion?t = the time taken to travel a distance of 100m.

v = the speed at which you travel.

t is inversely proportional to v t = k / v

t

v

Direct proportion?t = the time taken to build a wall.

N = the number of builders.

t is inversely proportional to N t = k / N

Inverse proportionT is inversely proportional to m.If T = 12 when m = 1, finda) T when m=2b) T when m = 24

kT

m

121

k 12k

12T

m

12) 6

2a T

12) 0.5

24b T

Inverse proportionT varies inversely as (y - 2).If e = 12 when y = 4, finda) e when y=6b) y when e = ½

( 2)

ke

y

122

k 24k

24

( 2)e

y

24) 6

(6 2)a e

241) 2 ( 2)b

y

50y