### Video Transcript

A car travelled a distance of 43.7
kilometres. It travelled at a speed of 532
metres per minute. How long was the car travelling
for? Round your answer to two
significant figures.

To answer this question, we need to
recall the formula triangle that connects the three quantities speed, distance, and
time. By covering up the quantity we wish
to calculate, so in this question that’s the time, we can see the formula that we
need to use: time is equal to distance divided by speed.

The distance travelled and the
speed are both given in the question. But if we look carefully, we can
see that the length units used are different: for distance, it’s kilometres, whereas
for speed, it’s metres. Before we can answer this question,
we need to convert to the same unit. So we we’ll convert the distance of
43.7 kilometres into metres.

To do so, we need to recall that
one kilometre is equal to 1000 metres. So to convert 43.7 kilometres into
metres, we multiply by 1000. 43.7 multiplied by 1000 is
43700. The calculation for the time taken
is, therefore, 43700 divided by 532. And we can use our calculator to
evaluate this. It’s equal to 82.142857 and the
decimal continues.

Now, the question asked us to round
our answer to two significant figures. And read that carefully — it’s
significant figures, not decimal places. The first significant figure is the
first nonzero digit in the number. So in this case, that’s eight. The second significant figure is
the next digit two. We need to look at one more figure
in the number to determine whether we should be rounding up or down. And as the next digit is a one,
this tells us that we’re rounding down. This gives a value of 82 and the
units for this time are minutes.