SRL Archive - Mathematics

So I have to do some work I haven't thought about in a while, and didn't listen to. Just some applications of systems of equations.

Daniel and Matt are selling cookie dough for a school fundraiser. They're selling sugar cookie dough and oatmeal cookie dough. Daniel sold 12 packages of sugar dough and 8 packages of oatmeal dough for $196. Matt sold 13 packs of sugar dough and 4 packs of oatmeal dough for $161.

Can someone just quickly show me how to set up the equation for this? I can solve it, I just forget that.

*whistles* Now I feel kinda stupid :p.

s = # of sugar cookie packages sold
o = # of oatmeal cookie packages sold

Daniel:

12s + 8o = 196

Matt:

13s + 4o = 161

But here's more to the question than that, so you should include that.

What do you mean there's more? All that's left is the question itself (find the cost).

Also, that's what I did and it didn't seem to work D:.

Because that's not a system of equations. It's a single inequality for two people. There's no more to do than that, other than guess and check.. Without more information, that is.

Oh no wait. One sec.

Just saying what my teacher told me xP.

12s + 8o = 196

(13s + 4o = 161) * -2

—

12s + 8o = 196

-26s + -8o = -322

—

(-26s = -322) * -1 (just because it's easier, imo.)

—

(26s)/26 = (322)/26

—

s = 161/13

—

12(161/13) + 8o = 196

—

1932/13 + 8o = 196

—

(1932/13) - (1932/13) + 8o = 196

—

(1/8) * (8o) = (616/13) * (1/8)

—

o = 77/13

—

12(161/13) + 8(77/13) = 196

—

(1932/13 + 616/13 = 196)13

—

1932 + 616 = 2548

—

2548 = 2548

S = 161/13 = $12.38
O = 77/13 = $5.92

That's all I needed. Thanks!

Hey-o!

In case you look at this again, I need some more help (again, on stuff I didn't listen to xD).

I need to graph a compound inequality after solving it:

49 < -6n + 1 <= -17

I've been searching google, but they all talk about it differently D:.

Edit again! I found it :D.

So you don't need help with that inequality or do you?

From: i luffs yeww
So you don't need help with that inequality or do you?

Just to make sure I did it right:


49 < -6n + 1 <= -17

49 < -6n + 1

Reverse it, so it looks better:

-6n + 1 > 49

Remove one, to get -6n by itself.

-6n > 48

Divide by -6.

n > -8

One of the two answers is n > -8.

-6n + 1 <= -17

Remove one to get -6n by itself.

-6n <= -18

Divide by -6 to get N by itself.

n <= -3

N <= -3 and n > -8

N is less than or equal to -3 and greater than -8.

Graph it (can't do it here) - closed dot for n <= -3, open dot for n > -8.

Check:

49 < -6n + 1 <= -17

Choose a number greater than -3, a number lower than -8, and a number that should match the equation.

I'll use -2.

-6(-2) + 1 = 13. Greater than 49? No. Less than -17? No. False.

For the second, -9.

-6(-9) + 1 = 55. Greater than 49? Yes. Less than -17? No. False.

For the third, -5.

-6(-5) + 1 = 31. Greater than 49? No. Less than -17? No. False.

Therefore, the inequality is false, and my answer is false, plus the graph.

I think I did that right. Knowing me I did it totally wrong.

Edit:

Looking at it, I realized that something can't be greater than 49 and less than -17 at the same time, saving me all the trouble of solving it. But I did it to make sure I understand it.

:) Just plug things back in to check.