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Anyone Wanna Help Me Out with some Math?

Senior Member

Joined: Aug 2009

Location: Next to the Maiden

Posts: 1,984

And after looking at the first one, I made a rookie mistake there.

It takes pipe A, running alone, 18 hours to fill the tank. It takes both pipes, running together, 9.9 hours to fill the tank. How long does it take pipe B, running alone, to fill the tank?

-----

A DATA:

time = 18 hrs/job ; rate = 1/18 jobs/hr

--------------------------------------------

A/B DATA:

time = 9.9 hrs/job ; rate = 1/9.9 job/hr

--------------------------------------------

B DATA:

time = x hrs/job ; rate = 1/x job/hr

----------------------------------------

Equation:

rate + rate = together rate

1/18 + 1/x = 1/9.9

---

9.9x + 9.9*18 = 18x

8.1x = 9.9*18

x = 22 hrs (time required by the B pipe to fill the tank)

Give me some slack, schools out. xD

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Joined: Apr 2009

Location: Australia, mate!

Posts: 8,419

I'm too good-looking to know these stuff.

hi
Senior Member
[Original Poster]

Joined: Dec 2008

Posts: 6,509

Quote:

Originally Posted by

**DGH94**
And after looking at the first one, I made a rookie mistake there.

It takes pipe A, running alone, 18 hours to fill the tank. It takes both pipes, running together, 9.9 hours to fill the tank. How long does it take pipe B, running alone, to fill the tank?

-----

A DATA:

time = 18 hrs/job ; rate = 1/18 jobs/hr

--------------------------------------------

A/B DATA:

time = 9.9 hrs/job ; rate = 1/9.9 job/hr

--------------------------------------------

B DATA:

time = x hrs/job ; rate = 1/x job/hr

----------------------------------------

Equation:

rate + rate = together rate

1/18 + 1/x = 1/9.9

---

9.9x + 9.9*18 = 18x

8.1x = 9.9*18

x = 22 hrs (time required by the B pipe to fill the tank)

Give me some slack, schools out. xD

Thanks, DGH. This clears it up. I eventually found the first one out on my own. Simple proportion

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So thaaaat's why I failed math.

back
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Joined: Aug 2009

Location: Next to the Maiden

Posts: 1,984

Quote:

Originally Posted by

**Kamazar**
Thanks, DGH. This clears it up. I eventually found the first one out on my own. Simple proportion

Np. I took Alg2AP this year and got an A, so I SHOULD know this. xD

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Posts: 8,419

How do I find the acute angle between y=2x and y=-2x?

hi
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Joined: Jul 2009

Posts: 1,398

Quote:

Originally Posted by

**Random_Guy**
How do I find the acute angle between y=2x and y=-2x?

Well you'd have to look for it I guess. When was the last time you saw it? And you've checked it's not in any of your pockets right?

**In-game name:**winegum

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Senior Member

Joined: Aug 2009

Location: Next to the Maiden

Posts: 1,984

Quote:

Originally Posted by

**Random_Guy**
How do I find the acute angle between y=2x and y=-2x?

If you're serious, what you want to do is draw a third line to make a right triangle. It should be the reciprocal of one of the lines if I remember correctly. Then find the distance of two of the sides of the triangle, and then use trig to find the angle needed.

BUT, the two equations you gave me don't form an acute angle, they form an angle of 120 degrees, an obtuse angle. So technically you're question is obsolete or I'm a complete retard.

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Joined: Feb 2009

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Posts: 5,549

Quote:

Originally Posted by

**DGH94**
If you're serious, what you want to do is draw a third line to make a right triangle. It should be the reciprocal of one of the lines if I remember correctly. Then find the distance of two of the sides of the triangle, and then use trig to find the angle needed.

BUT, the two equations you gave me don't form an acute angle, they form an angle of 120 degrees, an obtuse angle. So technically you're question is obsolete or I'm a complete retard.

then there's also an angle of 60deg

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