Question

Solving a Real-World Problem
The weather report says the temperature is 20°C and will drop 5°C per hour for the next 6 hours. Daryl plans to be gone for at least 6 hours, and he has a plant outside. If he wants the plant to remain in temperatures above –10°C, should Daryl move his plant to a warmer location before leaving?

An inequality to model the problem is
.
The solution is
.

Answer 1

Let t = hours gone. Temperature after t hours: 20 − 5t. He needs 20 − 5t > −10.

Inequality: 20 − 5t > −10.
Solve: −5t > −30 ⇒ t < 6.

Since he will be gone for at least 6 hours (t ≥ 6), the condition t < 6 is not met (at 6 hours the temperature is exactly −10), so he should move the plant to a warmer location.