Skill: Explain a solution using words

When you explain a solution, do more than give the answer. Tell:

1. What the numbers mean.
2. Which operation you use and why.
3. How the steps connect to the question.
4. Why your answer is reasonable.

Example:
A teacher has $4$ boxes with $(16)$ pencils in each box. She gives $(19)$ pencils to students. How many pencils are left?

Step 1: Find the total number of pencils.

There are $(16)$ pencils in each of $4$ equal boxes, so multiplication is needed:

$$4 \times 16 = 64$$

Using place value:

$$4 \times 16 = 4 \times 10 + 4 \times 6 = 40 + 24 = 64$$

This means the teacher started with $(64)$ pencils altogether.

Step 2: Subtract the pencils given away.

The teacher gave away $(19)$ pencils, so subtract:

$$64 - 19 = 45$$

There are $(45)$ pencils left.

Explain the answer in words:

I multiplied $4$ by $(16)$ because there were $4$ equal groups of $(16)$ pencils. This gave $(64)$ pencils in all. Then I subtracted $(19)$ because those pencils were given away. Therefore, the teacher has $(45)$ pencils left.

Check that the answer is reasonable:

Since $(4 \times 16)$ is $(64)$, and taking away about $(20)$ gives about $(44)$, an answer of $(45)$ makes sense.