Question

Which of the following is the next step while adding $8+9=17$ using the “make a ten” strategy?

• A. $7+9$
• B. $10+9$
• C. $8+10$
• D. $7+10$

Answer 1

The correct option is D $7+10$

Say: Let’s read the question.

Ask:
$\bullet$ Which of the given options can be an example of the “make a ten” strategy, and why?
Ans: All three options $A,B,$ and $C,$ because in all these three options, a number is added to $10$.
$\bullet$ How can we use the make a ten strategy to add $8$ and $9$ ?
Ans: To find $8+9,$ we break down $8$ into $7$ and $1,$ then add $1$ and $9$ to make $10,$ and finally add $7$ with $10$ to find the answer.
$\bullet$ Can option $D$ be a correct answer, and why?
Ans: No because $7+9$ can never be equal to $8+9.7+9=16$
$\bullet$ Can A and C be the correct option, and why?
Ans: No, because to find $8+9,$ after making a $10,$ we have to add $7$ with $10,$ not $8$ and $9$. Also, $8+10=18$ and $10+9=19,$ none of the total is equal to $17.$
Hence, option B is the correct answer.

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


Probing Question:
Q. Can we find $8+9$ using the doubles plus $1$ strategy?
A: Yes

Q. Which doubles can be used to solve it?
A: $8+8=16$

Q. How can we solve it?
A: We can solve it as shown below:
$8+9=8+8+1=16+1=17$