2.5 hours
I'm not sure of the correct formula but here is how I thought it through. Sally paints half the house and John paints half the house. So Sally would take 2 hours to paint her half and John would take 3 hours to paint his half. So it would take a max of 3 hours for the whole house to be painted because they'd be painting at the same time. But if you add the time it would take each of them to paint their half which would be 2 + 3 = 5 and divide that by 2 which would be the average of the two 5/2 = 2.5 hours. Okay so I take the long way around, but I'm pretty sure that is the right answer.
2006-06-26 07:01:11
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answer #1
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answered by pottersclay70 6
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I will assume you mean Sally can paint a house in 4 HOURS
Sally:
1 house = 4 hours
divide by 4:
1/4 house = 1 hour
multiply by x
x/4 house = x hours
This is the fraction of the house Sally can do in x hours
John
1 house = 6 hours
divide by 6:
1/6 house = 1 hour
multiply by x
x/6 house = x hours
This is the fraction of the house that John can do in x hours
Let x = time they work together(since they started at the same time, they will have equal time to work together, which is x)
In order to complete one house, the sum of the fractions of the house they can do in x hours must equal 1 whole house:
x/4 house + x/6 house = 1 house
Remove the units:
x/4 + x/6 = 1
Multiply by 12
3x + 2x = 12
Add
5x = 12
Divide
x = 12/5 = 2 2/5 hours
Therefore, it will take them 2 2/5 hours or 2 hrs. 24 mins. to paint the house.
Note: You can use this technique in every work problem you encounter (I developed it! If you need help, feel free to contact me!) But don't forget to use a different time for each if one started earlier than the other.
^_^
^_^
2006-06-26 23:47:38
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answer #2
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answered by kevin! 5
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4
2013-11-21 12:27:56
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answer #3
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answered by ? 1
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every hour Sally does 1/4 and John 1/6, that means together they paint 5/12 of the house in 1 hour. 1/(5/12)=12/5 or 2.4 hours.
Hope this helps!
2006-06-26 07:09:47
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answer #4
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answered by quickster94 3
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sally can paint 1/4 of the house in 1 hr and
John can paint 1/6 of the house in 1 hr
so (1/4 + 1/ 6)X = 1
where X = time for them to paint the house in hours
1/4 + 1/6 = 3/12 + 2/12 = 5/12
so 5/12X=1 and
X = 12/ 5 hr
2006-06-26 07:04:12
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answer #5
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answered by dhaval70 2
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5hours
sally paints 1/2 of the house in 2 hrs.
john paints 1/2 of the house in 3 hrs.
2+3=5
2006-06-26 07:10:11
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answer #6
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answered by Kim 3
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Sally paints 60% of the house, John 40%
John paints .4 house in .4*6 hrs = 2.4 hours
Sally, .6*4hrs = 2.4 hours
Synergy gets the house painted in 2.4 hours.
2006-06-26 07:02:29
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answer #7
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answered by bequalming 5
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5 hours
2006-06-27 00:30:58
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answer #8
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answered by Jordi L 3
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2 hours
2006-06-26 07:02:08
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answer #9
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answered by bz_co0l@rogers.com 3
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5 hours
2006-06-26 06:59:09
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answer #10
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answered by ? 4
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