Video Transcript
For the next three years, the
enrollment at a university is expected to increase by 55 students each year. If the university’s current
enrollment is 589 students, determine their enrollment in each of the next three
years.
In this question, we’re given some
information about the enrollment at a university. We’re told for the next three
years, the enrollment is going to increase by 55 students every year. And what this tells us is for the
next three years, every year there’s going to be 55 more students enrolled than the
last year. We’re also told that the current
enrollment is 589 students. We need to use this information to
determine the enrollment number in each of the next three years. To answer this question, let’s
start by looking at all the information we’re given.
First, we’re told that currently
there are 589 students enrolled at the university. Next, we’re also told that for the
next three years, the number of students enrolled is going to increase by 55 each
year. And there’s two different ways we
could think about this number. We could think about this is an
increase of 55 each year. So to answer this question, we just
need to add 55 to our value three times. However, we can also think about
this as the difference between enrollment rates in consecutive years.
We’re told that for the next three
years, this is a constant value of 55. And this tells us something useful
about the number of students involved in this university year by year. Since for these four years, the
difference between consecutive terms is constant. We call this an arithmetic
sequence, where the initial value or zeroth term of this sequence is 589 and the
common difference, 𝑑, is going to be equal to 55 because we’re increasing by 55
each year.
And this gives us another way of
answering this question because we know how to generate the 𝑛th term of an
arithmetic sequence. For an arithmetic sequence with
common difference 𝑡 and initial value 𝑎, the 𝑛th term is given by 𝑑 times 𝑛
plus 𝑎. We can use this to find the number
of students enrolled at our university for the next three years. For our arithmetic sequence, the
value of 𝑎 is 589 and the common difference 𝑑 is equal to 55.
So, we can calculate the number of
students enrolled after one year by substituting 𝑛 is equal to one into this
expression. We get 55 times one plus 589. And if we calculate this, we get
644. We can do the same to find the
number of students enrolled after two years. We use 𝑛 is equal to two. We get 55 times two plus 589, which
we can calculate is 699.
Finally, we’ll do exactly the same
for the number of students enrolled after three years. We substitute 𝑛, 𝑛 is equal to
three. This gives us 55 times three plus
589, which we can calculate is equal to 754. Therefore, we found the enrollment
of this university for the next three years. We get in the first year 644, in
the second year 699, and in the third year 754.
However, there is one thing worth
pointing out about our formula for finding the number of students enrolled after 𝑛
years. In this case, our formula is only
valid up to 𝑛 is equal to three. This is because in the question,
we’re only told that the number of students is going to increase by 55 for the next
three years. We don’t know what will happen
after four years or five years or any further years.
So, sometimes, in questions like
this, we do need to be careful about the exact information we’re given. For example, we would not be able
to use this formula to find the number of students enrolled at this university after
10 years. However, we were able to show that
in the next three years, the enrolment at this university will be equal to 644 after
one year, 699 after two years, and 754 after three years.
