Word problem

Deon588 · 2011-10-10 20:47:59

Hi all. Am I doing this correctly?
Question
In a factory 2 different machines A and B are used to fill bottles When the machines work together they fill the bottles in 2 hours. Machine A works twice as fast as machine B, how long does it take machine B to fill the bottles when it works alone? What i've done:

Deon588 · 2011-10-10 20:50:29

I see some of the LaTeX lines are very close to each other. Is there a way to avoid this? Or should I just leave a line open?
Thanks in advance

bobbym · 2011-10-10 20:57:48

I took care of the latex.

Did you check the answer you got?

Deon588 · 2011-10-10 21:54:36

Thanks a lot Bobbym. so

Bob · 2011-10-10 22:05:45

hi Deon588,

That looks good to me.

Bob

Deon588 · 2011-10-10 22:05:59

So it will take Machine B 4 hours to fill the bottles?

Bob · 2011-10-10 22:07:57

hi deon588

You've used x for how long B will take on its own and worked out x = 360 minutes.

That isn't 4 hours!

Bob

bobbym · 2011-10-10 22:50:29

Hi deon588;

How did you get 4 hours?

Deon588 · 2011-10-11 00:05:24

Hi Bob. That's the part which confuses me. isn't

Thanks a lot for checking

Bob · 2011-10-11 00:15:47

My answer:

Let x represent the time in minutes for machine B to fill N bottles.

measured in bottles/minute

and as A does the same number of bottles twice as fast

So working together

Cancelling the Ns and simplfying the LHS

Invert both fractions

So machine B takes 360 minutes or 6 hours.

Check. With no loss of generality I can suppose that N = 720.

Then B's rate per minute is 720/360 = 2 bottles per minute.

So A's rate must be 4 bottles per minute.

So together they can do 6 bottles per minute.

So they can do 720 in 720/6 minutes = 120 minutes = 2 hours. "tick"

Note: I was taught to start by introducing what x stands for. Look at my first line in bold text.

That makes it easier for someone to follow your working.

And at the end you know what you have worked out!!!

Bob

Last edited by Bob (2011-10-11 00:31:27)

Deon588 · 2011-10-11 10:50:58

Bob thanks a lot for that very detailed explanation, as usual u completely cleared it up for me:).

Bob · 2011-10-11 18:45:35

hi

That's good to know. It's a pleasure to be of help!

Bob

Math Is Fun Forum

#1 2011-10-10 20:47:59

Word problem

#2 2011-10-10 20:50:29

Re: Word problem

#3 2011-10-10 20:57:48

Re: Word problem

#4 2011-10-10 21:54:36

Re: Word problem

#5 2011-10-10 22:05:45

Re: Word problem

#6 2011-10-10 22:05:59

Re: Word problem

#7 2011-10-10 22:07:57

Re: Word problem

#8 2011-10-10 22:50:29

Re: Word problem

#9 2011-10-11 00:05:24

Re: Word problem

#10 2011-10-11 00:15:47

Re: Word problem

#11 2011-10-11 10:50:58

Re: Word problem

#12 2011-10-11 18:45:35

Re: Word problem

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