Video Transcript
Anthony made a train of 19
cubes. Which train has been correctly
decomposed into 10 ones and some more ones?
To begin with, we’re told that
Anthony made a train of 19 cubes. Now, if we ignore the colors for a
moment, a train of 19 cubes might look something like this. But the pictures that we can see in
the question don’t look like a train of cubes at all. Well, if we carry on reading the
question, we can see what’s happened to Anthony’s train. It’s been decomposed. This is a long word in maths, but
it means something very simple. It just means “split up.” So Anthony has taken his train of
19 cubes, and he split it up into 10 ones and some more ones. Which of the three pictures shows a
train that’s been split up into 10 ones and some more ones?
Let’s start off by thinking about
what might happen if we split a number up into 10 ones and some more ones. Of course, the number we’re
thinking of is the number 19. So here’s our group of 10 ones. Now, how many ones do we have
remaining? We have one, two, three, four,
five, six, seven, eight, nine ones. 10 ones plus nine more ones make
19.
Now, let’s imagine that Anthony
breaks apart or splits up his train into 10 ones and nine more ones. Which picture shows this? Well, we know it’s not going to be
the first picture, is it? There are lots more cubes there
than we need. But what about our second
picture? This shows a group of 10 cubes. And we don’t need to count the
second group because it’s one less than 10 we can see. It must be showing nine cubes. And because we know that 10 ones
and nine more ones go together to make 19, we know the picture that shows Anthony’s
train that’s being split up is the one that shows 10 ones and nine more ones.
