A focused Grade 6 learning session for Evaluating Expressions using visual models, worked examples, strategy guidance, and a short mastery check.
Student goal: I can solve problems involving evaluating expressions.
Evaluating Expressions means choosing a model, naming what each number means, and explaining the strategy.
Question: Which table shows correct values for the expression \(y=2x-1\)?
| \(x=1\) | \(x=2\) | \(x=3\) | \(x=4\) | |
|---|---|---|---|---|
| A: | \(0\) | \(3\) | \(5\) | \(7\) |
| B: | \(1\) | \(3\) | \(5\) | \(7\) |
| C: | \(2\) | \(4\) | \(6\) | \(8\) |
| D: | \(3\) | \(5\) | \(7\) | \(9\) |
Why it works: For each \(x\) value: \(x=1 \to 2(1)-1=1\); \(x=2 \to 2(2)-1=3\); \(x=3 \to 2(3)-1=5\); \(x=4 \to 2(4)-1=7\). Option B is correct.
Answer: B
Question: Evaluate \(4a-3b\) when \(a=5\) and \(b=2\).
Answer: \(14\)
Question: Find the value of \(6x+2\) when \(x=3\).
Answer: \(20\)
Question: Which student made an error in evaluating \(2x^2\) when \(x=3\)?
Why it works: Lexi incorrectly squared the entire expression \(2 \times 3\) before applying the exponent to just \(x\). The exponent applies only to \(x\), not to the coefficient \(2\).
Answer: Lexi
Evaluating Expressions becomes easier when students connect the question to a model, use clear steps, and explain why the answer fits.
Understand the model before choosing the operation.
Use scratch paper. The explanation matters more than simply seeing whether the choice is correct.
Evaluate \(4a-3b\) when \(a=5\) and \(b=2\).
Answer D: \(14\)
Substitute and compute: \(4(5)-3(2)=20-6=14\).
Find the value of \(6x+2\) when \(x=3\).
Answer C: \(20\)
Substitute \(x=3\): \(6(3)+2=18+2=20\).
Evaluate \(9-2y\) when \(y=1\).
Answer A: \(7\)
Substitute \(y=1\): \(9-2(1)=9-2=7\).
What is the value of \(\frac{3x}{2}\) when \(x=4\)?
Answer B: \(6\)
Substitute \(x=4\): \(\frac{3(4)}{2}=\frac{12}{2}=6\).
Evaluate \(5m-7\) when \(m=2\).
Answer A: \(3\)
Substitute \(m=2\): \(5(2)-7=10-7=3\).
Find the value of \(8+3n\) when \(n=5\).
Answer C: \(23\)
Substitute \(n=5\): \(8+3(5)=8+15=23\).
Evaluate \(p+q\) when \(p=7\) and \(q=9\).
Answer B: \(16\)
Substitute: \(7+9=16\).
What is \(2x+5y\) when \(x=3\) and \(y=2\)?
Answer D: \(16\)
Substitute: \(2(3)+5(2)=6+10=16\).
Evaluate \(10-a\) when \(a=3\).
Answer A: \(7\)
Substitute \(a=3\): \(10-3=7\).
Find the value of \(\frac{x}{3}+5\) when \(x=9\).
Answer C: \(8\)
Substitute \(x=9\): \(\frac{9}{3}+5=3+5=8\).
Evaluate \(100-6t\) when \(t=10\).
Answer A: \(40\)
Substitute \(t=10\): \(100-6(10)=100-60=40\).
