Video Transcript
The table shows five readings of
the distance traveled by a toy car that moved for 10 seconds. The distance was measured at
two-second intervals. Which color axis of the graph must
show the time that the car moves for? (A) Blue or (B) red.
Here, we’re given a graph and asked
to choose which axis, blue or red, represents the time that the car moves for. Let’s start by taking a look at the
data that the graph is representing, which is given to us in this table. We see that the top row of the
table is a set of times given in units of seconds, and the bottom row is a set of
distances moved given in units of meters. Each column of the table tells us
which time value and which distance value correspond to each other. For example, this column tells us
that at a time of zero seconds, the car had moved a distance of zero meters. This column tells us that after two
seconds, the car had moved a distance of five meters.
On the distance–time graph, each of
these pairs of values is represented as a single point. But this graph isn’t labeled with
very much information. To answer this question, we need to
work out which axis corresponds to the time the car moved for. We can do this by comparing the
graph to the information given in the table. All we really know about this graph
is that each axis starts at zero. We also know that the horizontal
axis has a maximum value 10 and the vertical axis has a maximum value of 25. Fortunately, this is enough for us
to work out our answer.
Let’s look at the last data point
on the graph. If we draw straight lines from this
point to each axis, we see that this point corresponds to a value of 10 on the
horizontal axis and a value of 25 on the vertical axis. So we know that this point
corresponds to the values of 10 and 25. But because we don’t know which
axis is which, we don’t know which value is the distance moved and which value is
the time. Did the car travel 10 meters in 25
seconds or did the car travel 25 meters in 10 seconds? To work this out, we need to look
back at the table. We need to find the column of the
table that has the value of 10 in one row and the value of 25 in the other. This is only true for this last
column. No other column contains both a 10
and a 25. Looking at this column, we see that
the 10 is in the time row and the 25 is in the distance moved row.
Now we can go back to the
graph. We know that this value of 10 must
be a time measured in units of seconds. We also know that this value of 25
must be a distance measured in units of meters. And just like that, we’ve labeled
the axes. We know that the red horizontal
axis shows us the time that the car has moved for, so this must be the correct
answer to this question. Answer choice (B) is correct. The red axis shows the time that
the car moves for. The other blue axis shows us the
distance moved by the car.
