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Ok, im going to make it up:

pat paints a fence in 2 hours, jill in 3 hours. put them together, how long does it take them for paint one fence.

1 hr and 12 mins, right?

2007-08-24 19:27:03 · 11 answers · asked by Trace 2 in Science & Mathematics Mathematics

11 answers

Yes. Fences = rate x time. Pat's fences = pat's rate x pat's time, so 1 = pat's rate x 2, so pat's rate = 1/2 fence per hour. Jill's fences = jill's rate x jill's time, so 1 = jill's rate x 3, so jill's rate = 1/3 fence per hour. Combining the rates, you get 1/2 + 1/3 = 5/6 fence per hour. 1 fence = 5/6 fences per hour x combined time, which is 6/5, which is 1 and 1/5 hour, which is 1 hour and 12 minutes.
There are other ways to do this but I took the dimensional analysis route.

2007-08-24 19:38:08 · answer #1 · answered by fenchurchthesane 6 · 0 1

pat paints a fence in 2 hrs, then in 1hr he can paint 1/2 of the fence. Samething with Jill, in 1hr, she can paint 1/3 of the fence.

Let t be the time it takes them to paint the fence together

(1/2)t + (1/3)t = 1
(5/6)t = 1
t = 1.2 hr or 1hr and 12min

you are correct!

2007-08-24 19:32:10 · answer #2 · answered by      7 · 0 1

work done by pat in 1 hr = 1/2
work done by jill in 1 hr = 1/3

if they do together then in 1 hour they do
1/2+1/3 = 5/6 of the work
now
5/6 work is done in 1 hour
so 6/6 =1 work is done in 6/5 * 1=6/5 hours
=1.2 hours

2007-08-24 19:33:43 · answer #3 · answered by sweet n simple 5 · 0 1

work finished in one hour

x = 1 work

1/2 x+ 1/3x = 5/6X

so they can do 5/6 of the job in hour

5/6 of X per hour

to finished the job

t = X/ rate
t = x/(5/6x)
t = 6/5 hour

1hr 12 min

2007-08-24 19:36:43 · answer #4 · answered by dbondocoy@yahoo.com 3 · 0 1

It will take them 1.2 hours to paint the fence together, or 1 hr 12 minutes.
Yes you are right.

2007-08-24 19:32:24 · answer #5 · answered by swd 6 · 0 1

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2016-10-16 22:26:18 · answer #6 · answered by ? 4 · 0 0

the workin is like this:
(a*b)/(a+b)
(2*3)(2+3)
6/5hours
1 hour and 12 minutes
yes , you're right

2007-08-24 19:31:34 · answer #7 · answered by **PiNoY YFC** 7 · 0 1

it's 1 hour 12 miniutes your right

2007-08-24 19:32:24 · answer #8 · answered by ashif_noohu 2 · 0 1

less than an hour or 50 mins

2007-08-24 19:34:43 · answer #9 · answered by darcey 3 · 0 2

YES !!! i suppose u'r just wasting 5 pts for this sice u are smart...

2007-08-24 21:09:12 · answer #10 · answered by Anonymous · 0 2

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