Answer:
4.5 hours (4 1/2 hours)
Step-by-step explanation:
Let's write out and solve an inquality:
$30 + ($80/hr)x ≤ $400
Note that $20/ 15 min is equivalent to $80/hr.
We need to solve for x.
Subtracting $30 from both sides of this equation, we obtain:
($80/hr)x ≤ $370
dividing both sides by ($80/hr), we get:
$370
x = ------------------- = 4.625 hrs
($80/hr)
Note that the photographer charges for every 15 minutes whether or not he is working during each 15 minutes. He will not pro-rate his charge. If you go over 4 1/2 hours of work, you will have to pay for another 1/4 hour (15 minutes), even if the total length of time the photographer works is less than 4 3/4 hours.
Thus, for $400 the longest photography session would be 4.5 hours, or 4 1/2 hours, for which Elena would pay $30 + ($80/hr)(4 1/2 hr) = $390. She would have $10 left over, because $10 would not be enough to pay for another full 15 minutes.
