Cogito
Grade 7 Math · Chapter 4 · Lesson 1
Adding Signed Numbers
A walk along the line.
10 problems · about 17 minutes · 7.NS.A.1
What this lesson teaches
The child adds rational numbers and explains the result as movement on a number line.
- Adding a positive walks right, a negative walks left.
- Additive inverses add to zero.
- Every case is one walk, so there are no sign rules to learn.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Finding the Original Price: £64 after 20% off. Original in pounds?
Answer 80
Why £80.
Review — Simple Interest: £600 at 5% for 2 years. Interest in pounds?
Answer 60
Why £60.
Warm Up
Straightforward practice. Get the method working first.
4 problems−9 + 4 = ?
Answer -5
Why −5.
What does adding a negative do on the line?
Answer Walks left.
Why Adding a negative moves left.
−5 + 9 = ?
Answer 4
Why 9 right from −5.
6 + (−10) = ?
Answer -4
Why 10 left from 6.
Build It Up
The same ideas with more to keep track of.
2 problems−3 + (−4) = ?
Answer -7
Why Left, then left again.
What is the additive inverse of −11?
Answer 11
Why It adds to zero.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Temperature: It is −7 degrees and rises 12. What is the temperature now?
Answer 5
Why 5 degrees.
The Account: An account at −40 pounds receives 15. What is the balance?
Answer -25
Why −25 pounds.