Question

Rameen’s heating bill is $5.42 per month plus $1.08 per therm. How many therms can Rameen use if he wants his heating bill to be a maximum of $87.50? Write the solution in interval notation.

Answer 1

Write and solve an inequality:

Total(t) = $5.42 + ($1.08/therm)(t) ≤ $87.50.

First, subtract $5.42 from $87.50:  then ($1.08/therm)(t) ≤ $82.08

Next, divide both sides by $1.08 per therm:

t ≤ ($82.08) / ($1.08/therm) = 76 therms (maximum).  Thus, Rameen's usage could be [0,76] (therms).