6th grade math

Joseph · 2008-03-11 11:06:35

A friend tells you she made 96, 83, and 87 on the past three math tests. What must she she make to get an average of 90.

Help!!!

(P.s. she has an average of 89 at first.)

Daniel123 · 2008-03-11 11:11:42

Rewriting that in mathematical form,

, where n is the score on the fourth test.

Joe Healy · 2008-03-12 21:33:15

I think your just supposed to figure that out with trial and error because I certainly didnt learn algebra in 6th grade.

So, if you dont know what that is:

n + 5 = 10 n in algebra could be any number and usually part of the eqaution (at your level anyway) is just to find out what n is.

n + 5 = 10 You can move the numbers around on this eqaution for example you could move the 5 over the = but you would have to change it to a negative

n = 10 - 5 now you can figure out what n is.

n = 5

now you check your answer by replacing n with 5

5 + 5 = 10 if its correct then you did the algebra correctly if its not then you stuffed something up go back and try and figure out what it was.

Try n + 5 - 7 = 4

the answer is n = 6 see if you can get that with working out. Geez if you can get that your doing better than I was in year 6 but hey im in Australia and our maths is notoriously easier than everywhere else so maybe its just me.

mathsyperson · 2008-03-13 08:23:03

If you want to work with smaller numbers, you could consider the distance of each of the given numbers from 90 and then work out what the last one needs to be for the total to be 0.

Taking 90 away from the three given marks gets 6, -7 and -3. These add to give -4, so the last number must give 4 when it has 90 taken away in order for the total to be 0.
Therefore, the last number is 94.

(Sorry if that didn't make sense to you.)

Math Is Fun Forum

#1 2008-03-11 11:06:35

6th grade math

#2 2008-03-11 11:11:42

Re: 6th grade math

#3 2008-03-12 21:33:15

Re: 6th grade math

#4 2008-03-13 08:23:03

Re: 6th grade math

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