00:00This video is part of a Google Form quiz that teachers can assign to their students for
00:05homework. After the students submit their answers, then they can play a video like
00:09this one to see the answer explained. We've made more than 100 quizzes as Google Forms
00:15with free access videos, which teachers are welcome to copy for free. To get access to these,
00:21please see the link in the description. This video is based on a question from an
00:26actual state exam. You may have one like this on your state exam. If you've not already watched the
00:32video on how to calculate the average, then we suggest that you view it before watching this
00:37video. A teacher recorded reading scores for three groups, which groups have the same mean score.
00:44We define the mean as the answer to a division problem. In everyday language, we use the word
00:50average instead of the word mean. The word mean is used on math tests and in math books,
00:56but has the same idea and formula as the word average. The mean of a set of numbers
01:02equals the sum of those numbers divided by the number count. Let's start by calculating the mean
01:07of group 1. There are three numbers in this group, so the number count for this set is 3.
01:13The sum of these numbers is the total of 15 plus 11 plus 19. That sum equals 45. Here's the formula for
01:21the mean. The mean equals the sum of the numbers divided by the number count. We substitute the
01:27phrase sum of numbers with 45. We substitute the phrase number count with 3. Then we do the division.
01:3545 divided by 3 equals 15. The mean for this group is 15. Next, let's calculate the mean of group 2.
01:44There are 5 numbers in this group, so the number count for this set is 5. The sum of these numbers
01:50is the total of 12 plus 14 plus 20 plus 14 plus 20. That sum equals 80. Here's the formula for the mean.
01:59The mean equals the sum of the numbers divided by the number count.
02:03We substitute the phrase sum of numbers with 80. We substitute the phrase number count with 5.
02:10Then we do the division. 80 divided by 5 equals 16. The mean for this group is 16. Next,
02:17let's calculate the mean of group 3. There are four numbers in this group, so the number count for this
02:23set is 4. The sum of these numbers is the total of 13 plus 19 plus 14 plus 14. That sum equals
02:3260. Here's the formula for the mean. The mean equals the sum of the numbers divided by the number count.
02:39We substitute the phrase sum of numbers with 60. We substitute the phrase number count with 4.
02:46Then, we do the division. 60 divided by 4 equals 15. The mean for this group is 15. Let's summarize what
02:55we found so far. The mean for group 1 is 15, the mean for group 2 is 16, and the mean for group 3 is 15.
03:03Group 1 and group 3 have the same mean, which is 15. Choice B is correct.
03:09Thanks for your attention.
03:20So
