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## 4th grade

### Course: 4th grade > Unit 14

Lesson 8: Converting units of time# Time word problem: Susan's break

Sal solves a time word problem and involves converting hours and minutes. Created by Sal Khan.

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## Video transcript

Susan has 96 minutes to
complete a test at school. The test begins at 1:59 PM. And Susan has volleyball
practice at 4:00 PM. How much time will Susan have
between the end of the test and the beginning of
volleyball practice? Let's think about
this a little bit. So the test begins at 1:59. So it's a very strange
time to begin a test, but let's just go with that. So let me draw a
little time line here. So let's say that
this is 2 o'clock PM. Then we're going
to have 3:00 PM. Then we're going to have 4
o'clock PM, which is also when volleyball practice begins. So this is volleyball practice. It's going to start then
and then go on from 4:00 PM. And then the test
begins at 1:59. So let me continue
the number line. So this right over
here is 1:00 PM. So the test is going to begin at
1:59, so 1 minute before 2 PM. We know that there are
60 minutes in an hour. So 1:59 is 1 minute
before 2:00 PM. So I'm not drawing it
completely it scale, but this right over
here is 1:59 PM. So we use 1 minute
to get to 2:00 PM. And then, let's see, we have
to get up to 96 minutes. So then you get another 60
minutes to go to 3:00 PM. So, so far, we've
used a cumulative 61. So this is 1 minute. So this is how long the
test has been going on since the beginning. So 1 minute by 2:00 PM,
61 minutes by 3:00 PM. If we go all the way to 4:00 PM,
that's going to be another 60. That'd be 121 minutes, which
is longer than the actual test. So we know that the
entire test is 96 minutes. So we're going to get
to some point right over here, some point like this. That's 96 minutes. And what we need to figure
out is, is what is left over? What is this distance
right over here? Or what is this
time, this difference in time right over here? And so to figure
that out, we had to figure out the time at
which 96 minutes have passed since the beginning of the exam. So at 3 o'clock, 61
minutes have passed. And so if we, if we say
well how many more minutes have to go on for
the end of the test? It's going to be 96 minus 61. So the amount of time that
elapses past 3 minutes is 96 minus 61,
which is 35 minutes. So this right over here
is going to be 3:35. And so now our question
is, how much time is there between 3:35 and 4:00 PM? Well, once again, 60
minutes in an hour. 4:00 PM is essentially
the 60th minute. So if we take 60
minus 35, we get 2:25. So she has a total of 25
minutes remaining after the test before she has to get
to volleyball practice. Just as a review. One minute between 1:59
and 2:00, then another 60. That gets us to
61 total minutes. Then another 35 minutes gets
us to 96 minutes have passed. And that also gets
us to 3:35, which means we have 25
minutes until 4:00.