Suppose that d varies jointly with r and t, and d = 110 when r = 55 and t = 2. Find r when d = 40 and t = 3.

r = 13.33

Step-by-step explanation:

d = k*r*t

Where,

k = constant of proportionality

d = 110 when r = 55 and t = 2

d = k*r*t

110 = k * 55 * 2

110 = 110k

k = 110/110

k = 1

Find r when d = 40 and t = 3

d = k*r*t

40 = 1 * r * 3

40 = 3r

r = 40/3

= 13.333333333333

Approximately,

r = 13.33

john earns $14.00 for two hours of work.