Cogito
Grade 6 Math · Chapter 5 · Lesson 2
Letters for Numbers
A variable stands for a number you do not know yet.
10 problems · about 17 minutes · 6.EE.A.2
What this lesson teaches
The child writes and evaluates algebraic expressions and reads expressions in words.
- A variable is a letter standing for a number.
- 2n means 2 multiplied by n.
- Substituting puts a value in and works the expression out.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Exponents and Order of Operations: What is 5 + 2 × 3²?
Answer 23
Why 23.
Review — Distance on the Coordinate Plane: Distance from (−3, 2) to (5, 2)?
Answer 8
Why 8 units.
Warm Up
Straightforward practice. Get the method working first.
4 problemsIf a = 8, what is 4a − 5?
Answer 27
Why 27.
What does 2n mean?
Answer 2 multiplied by n.
Why A number written against a letter multiplies it.
If x = 4, what is 5x?
Answer 20
Why 5 × 4.
If x = 5, what is 2x + 7?
Answer 17
Why 10 + 7.
Build It Up
The same ideas with more to keep track of.
2 problemsIf y = 3, what is y²?
Answer 9
Why 3 × 3.
If n = 10, what is 3n − 4?
Answer 26
Why 30 − 4.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsSubstituting: If n = 6, what is 3n + 2?
Answer 20
Why 20.
The Perimeter: A square has side s. If s = 9, what is 4s?
Answer 36
Why 36.