Video Transcript
Is eight the answer to both these
sums? Eight plus zero equals what? And zero plus eight equals
what?
This is a really interesting
question because, in a way, we’re given the answer before we start. We’re given two addition sentences
and then asked, is eight the answer? It’s our job to look at the sums
and to think to ourselves, is the answer eight both times?
To begin with, let’s look at our
additions. What do we notice? Well, the first thing that we can
see is that they both contain the same two numbers being added together. There’s a number eight and there’s
a zero. Remember that zero has a value of
nothing; it’s not worth anything. We can also see that both number
sentences are additions. That’s why the word sums is used in
the question. It means additions, two numbers
added together.
So, they both contain the same
numbers. They both contain addition
symbols. But the numbers in each sum are the
other way around. Did you notice this? In the first calculation, we start
with eight and then we add on zero. And in the second sum, we start on
zero and we add eight. So, do you think eight is gonna be
the answer to both these sums?
Let’s use a number track to help us
model what they’re asking us. In our first sum, we need to work
out the answer to eight plus zero. So, the number we’re going to start
on is the number eight. We’ll put a counter next to the
number eight to show where we’re starting from. And now, we need to move on another
zero places because we’re adding zero. Watch the counter. We’re about to move it zero
places. There we are. It hasn’t moved at all. We know it’s not going to move
because zero is the same as nothing, no places.
If we add a zero to a number, it
stays the same. So, if we start on eight and we add
nothing to it, we get an answer of eight. So, we know that eight is the
answer to the first sum. But is it the answer to both of the
sums? Let’s check out the second sum.
In this addition, we need to start
on zero and count on another eight because we need to add eight to it. Our number line has the number zero
on it already, so let’s put a counter next to it. Now, let’s move it eight places as
we add eight. We’ve moved it one place, two
places, three, four, five, six, seven, eight. If we start with zero and add
eight, we get an answer of eight.
This question shows us a really
interesting fact about adding with zero. If we start off with a number and
we add zero, the number stays the same. And if we start on zero and we add
a number, the answer is going to be the same as the number we added. Eight plus zero equals eight. And if we add the two numbers the
other way around, zero plus eight also equals eight. Our counters ended up in exactly
the same place. Is eight the answer to both these
sums? Yes, it is.
