Video Transcript
Liam is subtracting from seven. Write the missing number
sentence. Seven take away one is six. Seven take away two is five. Seven take away three is four. Seven take away four is three. What? Seven take away six is one.
In this question, Liam is taking
away or subtracting from the number seven. We know this because we’re told
this in the first sentence. We can also see that on each of his
ten frames, he’s put seven black counters to start off with. And we can also see that the first
number in every number sentence is seven. It’s the number Liam is starting
off with each time. And so the first thing we can say
about our missing number sentence is it’s going to begin with the number seven. What’s the next thing we can
say?
Well, because this is a subtraction
number sentence, we need to take away a number. But how many should we take
away? If we look carefully at Liam’s
pictures, we can see that he’s taking away in a certain order. In the first ten frame, he’s
crossed out or taken away one counter, then two counters in the second ten
frame. Then he takes away three, then
four. He’s taking away one more each
time, isn’t he? And one more than four is five. Our missing number sentence shows
seven take away five.
Now, we could find the answer by
counting the number of black counters that haven’t been taken away. But we could also find the answer
by looking at our number sentences, in particular, the answers. Our first answer is six, then five,
four, three. Can you see a pattern here? Liam is taking away one more
counter each time. And so his answer is getting one
less each time. His last answer was three. So his next answer, the one we’re
looking for, is going to be one less than three. We would expect it to be two.
Now, does that number sentence make
sense? Is five and two a pair that make
seven? Yes, they are. Liam’s missing number sentence is
seven take away five is two.
