Question

The Bernards are trying to determine their babysitter's rates but are to embarrassed to just ask her. They were charged $20 for 2 hours last week, but only $31 for 4 hours this week. What is the formula to determine A(Amount) given t(time in hours)?

Answer 1

A = 5.5t + 9

Explanation:

We assume that the relationship between t and A is linear.

We have two points on a line: (2, 20) and (4, 31).

We now find the equation of the line.

A = mt + b

m = (31 - 20)/(4 - 2) = 11/2 = 5.5

20 = 5.5(2) + b

20 = 11 + b

b = 9

A = 5.5t + 9