# Thread: Out of 20 probelms two are driving me crazy.

1. ## Out of 20 probelms two are driving me crazy.

This homework, and it's not graded by problem, its graded on completed the assignment and turning it in. I know you guys are thinking, "well you got it easy. But, it comes back to hunt you, trust me. Because the teach does not grade each question and just the assignment your kind of stuck making sure you understand the formula by test time on your own. The answers are in the back of the book, but the problem is, I have no idea how to get to the answer. I keep screwing up and ending up with something else.

Could someone help and kinda map out and explain in short, but understandable detail as to how you solved it. I know it will more then likely be on this weeks exam and I really need at least a B. I been doing bad lately.

12. Suppose m varies directly as t. If m = 13 when t = 2, then what is m when t = 6.

13. If y varies inversely as r and y = 9 when r = 3, then what is y when r = 9.

2. Originally Posted by B3astiie

12. Suppose m varies directly as t. If m = 13 when t = 2, then what is m when t = 6.

t changes by a factor of 3 ... so, how would m change if m varies directly as t ?

13. If y varies inversely as r and y = 9 when r = 3, then what is y when r = 9.

r changes by a factor of 3 ... since y varies inversely as r, wouldn't y change by a factor of 1/3 ?

...

3. Originally Posted by skeeter
...
Wait wait wait.

so lost.

4. Wait hold on I think I got it, give me just a second

5. 12. Suppose m varies directly as t. If m = 13 when t = 2, then what is m when t = 6.

13. If y varies inversely as r and y = 9 when r = 3, then what is y when r = 9.
Part 1:

m/t = 13/2
2m = 13t
2m = 13(6)
m = (13*6)/2 = 39

Or:
6/2 = 3 so 3*13 = 39

Part 2:

yr = 9*3
y = 27/r
y = 27/9 = 3

Or:
r2 / r1 = 9 / 3 = 3
y = 1/r = 1 / 3
So y is 1/3 of r2 which is 3.

Patrick

6. 13/2 = t/6

when using the proper forumla it becomes

19/2 =t

is 12. 19/2 equals y?

7. oh crap, I see what I did wrong I'm adding instead of multiplying. god I'm stupid or slow. I should of known that.

8. It happens to all of us. I still do stuff like that all the time.

9. I think I'm burnt out. Been working 3 jobs for christ and going to school part-time, just got done with a 7 page paper.

I don't know why it didn't cross my mind I was adding and not multiplying. I appreciate it alot brother.