Question

When subtracting $12$ from 18 using the ‘make a $10$’ strategy, which of the following pair of equations can be used?

• A. $18-8=10,10–4=6$
• B. $18-8=10,10–8=2$
• C. $12-2=10,10–7=3$
• D. $12+6=18,10–12=2$

Answer 1

The correct option is A $18-8=10,10–4=6$

Say: Let’s read the question.

Ask:
$\bullet$ What is the first step to subtract $12$ from $18$ using the make a ten strategy and why?
Ans: We break down $12$ into $8$ and $4$ because we can make a $10$ by subtracting $8$ from $18.$
$\bullet$ What is the next step?
Ans: We subtract $8$ from $18$ to make $10.$
What do we do next?
Ans: We subtract $4$ from $10$ to get $6$ as the answer.
$\bullet$ What will be the required correct equations for the question?
Ans: $18-8=10,10–4=6$
Hence, option A is the correct answer

WB: If required, use the whiteboard to show the solution

Probing Question:
Q. If we break down $18$ into $8$ and $10$ instead of splitting $12$ into $8$ and $4,$ will it still be a make a ten strategy?
A: If we split $18$ into $8$ and $10,$ we will be unable to subtract $12$ from either of the numbers as both are less than $12.$ So, we will have to further split $12$ to subtract. Hence, it will not be a make a ten strategy anymore.