There was nothing special about these particular numbers. This always works!

  • A positive times a positive is always positive.
  • A negative times a positive or a positive times a negative is always negative.
  • A negative times a negative is always positive.

Practice

Exercise (PageIndex{5})

Fill in the missing numbers in these equations

  1. (-2cdot (-4.5)=?)
  2. ((-8.7)cdot (-10)=?)
  3. ((-7)cdot ?=14)
  4. (?cdot (-10)=90)

Exercise (PageIndex{6})

A weather station on the top of a mountain reports that the temperature is currently (0^{circ} ext{C}) and has been falling at a constant rate of (3^{circ} ext{C}) per hour. If it continues to fall at this rate, find each indicated temperature. Explain or show your reasoning.

  1. What will the temperature be in 2 hours?
  2. What will the temperature be in 5 hours?
  3. What will the temperature be in half an hour?
  4. What was the temperature 1 hour ago?
  5. What was the temperature 3 hours ago?
  6. What was the temperature 4.5 hours ago?