1
00:00:00,713 --> 00:00:05,949
In a language class, the girl to boy ratio is 5 to 8.

2
00:00:05,949 --> 00:00:09,536
So for every 5 girls, we have 8 boys.

3
00:00:09,536 --> 00:00:13,247
If there are a total of 65 students,

4
00:00:13,247 --> 00:00:15,576
how many girls are there?

5
00:00:15,576 --> 00:00:16,576
So this is interesting.

6
00:00:16,576 --> 00:00:19,131
They give us the ratio of girls to boys.

7
00:00:19,131 --> 00:00:20,900
But then they want us to think about how many

8
00:00:20,900 --> 00:00:24,803
girls there are given that there are 65 total students.

9
00:00:24,803 --> 00:00:26,313
So what we really want to think about

10
00:00:26,313 --> 00:00:28,977
is not just the ratio of girls to boys – we want

11
00:00:28,977 --> 00:00:36,536
to think about the ratio of girls to total students.

12
00:00:36,536 --> 00:00:37,523
So how can we figure out

13
00:00:37,523 --> 00:00:39,727
what this ratio's going to be?

14
00:00:39,727 --> 00:00:42,870
Well the girl-to-boy ratio gives us a good clue.

15
00:00:42,870 --> 00:00:48,306
If there are 5 girls for every 8 boys, how many total

16
00:00:48,306 --> 00:00:51,403
students are there going to be for every 5 girls?

17
00:00:51,403 --> 00:00:54,604
Well for every 5 girls, you're going to have

18
00:00:54,604 --> 00:00:56,809
5 girls and 8 boys.

19
00:00:56,809 --> 00:00:58,995
You're going to have 13 total students.

20
00:00:58,995 --> 00:01:01,246
So I just added the 5 and the 8 right over here.

21
00:01:01,246 --> 00:01:04,836
The ratio of girls to total students is 5 to 13.

22
00:01:04,836 --> 00:01:06,844
One way of thinking about it is if you were

23
00:01:06,844 --> 00:01:10,453
to evenly divide the students into groups of 13,

24
00:01:10,453 --> 00:01:14,710
every group of 13 students would have 5 girls.

25
00:01:14,710 --> 00:01:16,573
Now, I think we're ready to figure out

26
00:01:16,573 --> 00:01:19,172
how many total girls there are.

27
00:01:19,172 --> 00:01:24,965
Because they tell us that there are 65 students.

28
00:01:24,965 --> 00:01:27,130
So, we don't just have one group of 13,

29
00:01:27,130 --> 00:01:29,003
we have 65 students.

30
00:01:29,003 --> 00:01:31,630
And how many groups of 13 are in 65?

31
00:01:31,630 --> 00:01:38,037
Well to go from 13 to 65, you have to multiply by 5.

32
00:01:38,037 --> 00:01:41,431
5 × 10 is 50 and 5 × 3 is 15. Right.

33
00:01:41,431 --> 00:01:43,365
So, 13 × 5 is 65.

34
00:01:43,365 --> 00:01:45,078
So essentially, one way you could view it is

35
00:01:45,078 --> 00:01:47,284
you have 5 groups of 13.

36
00:01:47,284 --> 00:01:48,925
So if you have 5 groups of 13,

37
00:01:48,925 --> 00:01:51,018
each of those are going to have 5 girls.

38
00:01:51,018 --> 00:01:56,441
Multiply by 5, and you're going to have 25 girls.

39
00:01:56,441 --> 00:01:58,113
So for every 65 students,

40
00:01:58,113 --> 00:02:00,171
you're going to have 25 girls,

41
00:02:00,171 --> 00:02:03,722
given the information that has been given.