Video Transcript
Daisy goes jogging every day. If she jogged for seven hours this
week, complete the given table.
We can see that the first row of
our table shows the days of the week. So there are seven separate
columns. And for each day of the week, in
our second row of the table, it shows the number of hours that Daisy spends jogging
each day. Well, all apart from one day, we
can see that Saturday’s time is missing. The question tells us that Daisy
jogged for seven hours this week. So we need to use this fact to help
us work out how many hours that she jogged on Saturday. We know she definitely did jog on
Saturday because she goes jogging every day.
To start with, let’s calculate how
many hours we can see in the table at the moment. On Monday, Daisy jogged one
hour. On Tuesday, she jogged another
hour. That’s a total, now, of two
hours. Let’s make a note of that. She jogged another hour on
Wednesday. So that’s three hours now in
total. Another hour on Thursday. On Friday, she jogs 0.5 hours. That’s the same as half an
hour. And if we add 0.5 to four, we get a
total of 4.5 or four and a half hours. We don’t know what Saturday’s time
is. But we do know that Daisy jogged
one more hour on Sunday.
So at the moment, our table shows
that she jogged 5.5 or five and a half hours. But the question tells us that
Daisy jogged for seven hours this week. To find out how many hours Daisy
jogged on Saturday, we need to subtract 5.5 from seven. Now, there are several ways we
could find the answer to this. For example, we could start with
5.5 hours and count on until we get to seven. We could use a number line to help
us. But in this video, we’re going to
use the column method. Let’s subtract 5.5 from seven.
Now, if we look carefully at our
subtraction, we don’t have anything in the tenths place in the first number. It’s just the number seven. But this is going to make it
difficult for us. We need to subtract from something
in the top number. So we need to write a decimal point
and use zero as a placeholder. The number is still seven, but now
we can subtract five-tenths. And the way we’re going to subtract
five-tenths is by exchanging. We can’t take away five-tenths from
zero. So we can take one one — instead of
seven ones, we now have six ones — and exchange it for ten-tenths. Because we know ten-tenths are the
same as one one. Ten-tenths take away five-tenths
leaves us with five-tenths.
Now, as we move along from right to
left, let’s make sure we put the decimal point so it’s aligned with the other
decimal points. Now, we just need to subtract the
ones. Six take away five equals one. The remaining amount to take us
from 5.5 up to seven is one and a half hours or 1.5. And so, if Daisy jogged for seven
hours this week, we need to complete the table using the number 1.5.
