Video: Identifying the Subtraction Expression That Is Not Equal to a Given Number

Which of these is NOT equal to 9? [A] 12 − 2 [B] 10 − 1 [C] 17 − 8 [D] 14 − 5 [E] 15 − 6


Video Transcript

Which of these is not equal to nine? 12 take away two. 10 take away one. 17 take away eight. 14 take away five. 15 take away six.

Let’s start by checking 12 take away two. We could partition number 12 into 10 and two. And if we were to take away the two, we would have 10 left. 12 take away two equals 10. So, the first expression is not equal to nine. Is 10 minus one equal to nine? Well, here, we have 10 counters in our 10 frame. And if we take away one, we will be left with nine. 10 take away one equals nine.

Does 17 take away eight equal nine? Well, we can partition 17 into 10 and seven. We can take away the seven. One, two, three, four, five, six, seven. That leaves us with 10. But we need to take away eight, so we have to take away one more. 17 take away eight is nine.

Does 14 take away five equal nine? Well, we can partition 14 into 10 and four. Take away the four to leave us with 10. And then, take away one more, which will leave us with nine. 14 take away five equals nine. If we have 15 and we take away six, we’ll also be left with nine. 15 take away five is 10, take away one more is nine. All of the expressions equal nine, except the first one. The expression which is not equal to nine is 12 take away two.

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