# Tutor.com Elementary Statistics Session

##### May. 22, 2012

Session Transcript - Math - Algebra, 3/25/2012 6:20PM - Tutor.comSession Date: 3/25/2012 6:20PM
Length: 11.1 minute(s)
Subject: Math - Algebra

System Message
[00:00:00] *** Please note: All sessions are recorded for quality control. ***

Guest (Customer)
[00:00:00] Amy received grades of 85, 87, 88, and 92 on her math tests. What must her grade be on her next test if her average is sto be at least 90?

Ellen C (Tutor)
[00:00:07] Welcome to Tutor.com ! Let's get started.

Guest (Customer)
[00:00:12] Okay.

Ellen C (Tutor)
[00:00:27] You indicated you have no idea where to start...

Guest (Customer)
[00:00:32] Yes.

Ellen C (Tutor)
[00:00:35] remember that, to find an average,
[00:00:49] we add up our data points, and divide by the number of data points....
[00:00:53] for example,
[00:01:50] if there were five numbers we wanted to average, we'd add them up, then divide by five. Does that make sense?

Guest (Customer)
[00:01:58] Yep.

Ellen C (Tutor)
[00:02:02] ok, gret!
[00:02:04] *great!
[00:02:09] so, for amy's tests,
[00:02:24] she has four scores already.
[00:02:37] we want to make sure the average of her *5* scores will be at least 90.
[00:02:45] so, we can setup like this:
[00:03:38] now, we don't know her fifth test score - that's what we're trying to find -
[00:03:41] so let's call it x.
[00:03:50] does that make sense?

Guest (Customer)
[00:03:53] Yes.

Ellen C (Tutor)
[00:03:58] great!
[00:04:06] so now, all we have to do is solve for x.
[00:04:11] do you know how we would do that?

Guest (Customer)
[00:04:19] ultiply both sides by 5
[00:04:23] mulitply*

Ellen C (Tutor)
[00:04:28] good start!
[00:04:58] what next?

Guest (Customer)
[00:05:14] we add al th enumbers together and subtract them to the other side, leaving x

Ellen C (Tutor)
[00:05:28] great! what does that give us?

Guest (Customer)
[00:05:33] 352
[00:05:56] 450-352 = 98

Ellen C (Tutor)
[00:06:01] excellent!
[00:06:25] so, in order to have an average of at least 90 after the fifth test,
[00:06:34] she needs to score at least a 98 on the next test.
[00:06:40] Does this problem make sense to you now?Â

Guest (Customer)
[00:07:15] yes. but if the problema sks for at least? would the sign be an inequality instead of an =?

Ellen C (Tutor)
[00:07:56] sure that means that our equal sign would be a less than or equal sign.

Guest (Customer)
[00:08:29] why is it less than or equal to? shoudlnt it be greater than 98 or equal?

Ellen C (Tutor)
[00:09:05] no, as we said above, her score must be "at least" 98.
[00:09:15] so that means that x has to be 98 or more,
[00:09:25] so 98 is less than or equal to x.
[00:09:33] oh, i see, you reversed them.
[00:09:36] yes, you could also say
[00:09:43] x greater than or equal to 98.

Guest (Customer)
[00:09:48] Oh, i get it. Thanks for clearing that up

Ellen C (Tutor)
[00:10:06] sure thing sorry, I was just going by what we had on the board.