### Video Transcript

Which of the following would be the
best estimate for the amount of time it would take to climb a flight of stairs? 30 minutes, 30 seconds, or 30
hours?

Before we start to think about
answering this question, what do you notice about the possible answers that we’re
given? Can you see each of these
measurements of time contains the same number, 30? But the unit of measurement, that’s
a thing we’re measuring time in, is different each time. So this question is really about
whether you know what a minute, a second, and an hour is.

Now, our question’s all about the
amount of time it takes to climb a flight of stairs. Maybe you live in a house that has
stairs in it. At the end of the night, when it’s
time to go to bed, how long does it take you to get from the bottom of the stairs to
the top? There’s an interesting word in this
question, and it’s the word “estimate.” An estimate is a thoughtful
guess. In other words, we don’t need to
know the exact amount of time it takes you to walk up a flight of stairs. But what we want is a good guess, a
guess that we’ve thought carefully about so that it makes sense.

Do any of these amounts of time not
make sense? We know that an hour is about the
length of time that you have for your lunch time every day. So do you think it would take 30
lunch times to get from the bottom of the stairs to the top? Of course, not. That doesn’t make sense, does
it? That’s a silly answer. This isn’t the best estimate at
all.

The answer is going to have to be
30 minutes or 30 seconds. Which is the best estimate? Well, we know that there are 60
minutes in an hour, so 30 minutes is half of an hour. Does this sound right, that you
start climbing the stairs and then half an hour later, you reach the top?

Well, what about 30 seconds? We know that 30 seconds is about
the length of time it takes to count to 30. Which units of measurement would
make the best estimate? It’s 30 seconds, isn’t it? If we started counting from 1 to
30, it makes sense that we might reach the top of the stairs by the time we got to
30. 30 minutes and 30 hours are far too
long. The best estimate for the amount of
time it would take to climb a flight of stairs is 30 seconds.