Video Transcript
16 plus three is 19. Which number sentence is missing
from the number sentences three plus 16 equals 19, 16 plus three equals 19, and 19
take away 16 equals three?
It seems from this question that we
got a missing number sentence here. We’re given a family of three
different number sentences, but there must be a fourth one that we need to find. To begin with, we’re given a number
fact. 16 plus three is 19. We know we could model this using
cubes. 16 plus three is 19. And if we look at our number
sentences that we’re given, the second one shows this number fact written as a
number sentence 16 plus three equals 19. Now, we can use these three
numbers, 16, three, and 19, to write a family of addition and subtraction facts
because 16 and three are two parts that make a whole amount, 19.
And you know, we could make that
whole amount in one other way. If we look at our train of cubes,
we could just swap the pink and the orange cubes around. Three plus 16 is 19 too. And this is where we get our first
number sentence from. So we start off with two
additions. Our final number sentence is a
subtraction, and we can see the same three numbers again. This time, we’re starting with the
whole amount. If we have 19 and we take away 16,
we’re left with three. So we have two additions, but we
only have one subtraction.
Let’s try and find another
subtraction that we could make using these numbers. We know the whole amount is 19. So if we’re going to take away a
number, we need to start with this whole amount. Let’s make 19 the first number in
our number sentence. And we’re going to look for another
subtraction. So we need to use the subtraction
symbol. Now, we need to take away one of
the parts. In the subtraction we’re already
given, we’ve taken away 16. So instead of taking 16, let’s take
away three.
19 take away three equals what? Well, we know from that very first
number fact that 16 and three go together to make 19. And so if we start with 19 and we
take away three, we’re going to be left with 16. We can use one addition fact to
write a whole family of addition and subtraction facts. The number sentence that’s missing
is 19 take away three equals 16.
