### Video Transcript

Fill in the blank: The mass of the
puppy is what kilograms.

In the picture, we can see a set of
balancing scales. This is the sort of equipment we
can use to help weigh the mass of different objects. In this case, we’re using them to
measure the mass of a puppy. And we can see the puppy at one end
of our measuring scales. And at the other end, we have what
look like some metal weights. Can you see what’s written on
them? Each of the weights is labeled one
kg or kilogram. So how many kilograms are at this
end of our scales? There are four of them. Each one is worth one kilogram, so
we can say that there are four kilograms altogether.

Now our question asks us to fill in
the blank with the mass of the puppy. In other words, how heavy does the
puppy weigh? Well, we could just look at our
kilogram weights and say it weighs four kilograms. And that it’s actually the right
answer. But before we say that, we need to
think carefully. Why is the mass of the puppy four
kilograms? And it’s not just because four
kilograms are on the other end of our scales.

These scales have four kilograms at
one end and a puppy at the other. But on these scales, the puppy is
lower than the four kilograms. If our scales look like this, we
would know that the puppy was heavier than four kilograms. It would weigh more than four
kilograms. And if our set of scales look like
this, again, we’d still have four kilograms on one end and a puppy on the other. But this time, it’s the four
kilogram weights that’re heavier. This end of our set of scales is
pushed down. The puppy is lighter than four
kilograms. And so in this example, we would
say that the puppy is less than four kilograms.

Now, let’s come back to our
picture. How would you say we know that the
mass of the puppy is four kilograms? Yes, there are four kilograms at
one end and a puppy at the other. But the important thing is that our
scales are balanced; both ends of the scale weigh the same. The mass of the puppy is equal to
four kilograms. Can you see how they’re both level
with each other? We didn’t just find the answer by
counting the number of kilograms. We looked at the fact that our
weighing scales were balanced. And we know now that the mass of
the puppy is four kilograms.