Meet Mrs. Rowe
Mrs. Rowe's "Theorem"
Working with Subtracting Integers.
What does KFC mean?
K Keep it
F Flip to add
C Change the sign
When students apply the KFC rule, they can easily work with subtracting both positive and negative numbers. Let's take a look:
-3 - 5 is the same as -3 (Keep it) + (Flip to add) -5 (Change the sign). So that's -3 + -5. When signs are the same, you add and keep signs. Answer is -8!
3-5. So that's 3 (Keep it) + (Flip to add) -5 (Change sign). So that's 3+-5. Since signs are different, find the difference and sign is largest absolute value. Answer is -2!
One final example:
-3 - -5. -3 (Keep it) + (Flip to add) 5 (Change sign). That is now -3 + 5. Signs are different so find the difference and sign is largest absolute value. Answer is 2!
Real World Applications
Temperature. Temperature was 15 degrees at noon and dropped 20 degrees by 6:00PM. 15-20 is 15 + -20. Temperature at 6:00PM was -5 degrees.