Bob and Bill were washing cars. Bob can wash a car in 6 minutes. Bill can wash a car in 8 minutes. How long will it take if Bob and Bill wash a car together?
P.S. The answer is NOT 7.
2007-09-26 14:44:07 · 20 answers · asked by abcw 3 in Science & Mathematics ➔ Mathematics
well Bill is faster at washing a car, so he would do more than half the work when the two washed them together. But I don't know the answer...sorry
2007-09-26 14:46:58 · answer #1 · answered by Anonymous · 0⤊ 1⤋
Ok...Bill can wash a car alone in 8 minutes. Bob can do it in 6 minutes. Let x be the amount of time it takes to wash one car together. Now, Bill can wash 1/8 of a car in one minute and Bob can wash 1/6 of a car. Thus, together, these would have to add up to 1/x as follows....
1/6 + 1/8 = 1/x
Solve for x
7/24 = 1/x
x = 24/7
x = 3.43 minutes (approximately 3 minutes, 26 seconds)
Hope that made sense.
2007-09-26 21:57:55 · answer #2 · answered by john 3 · 0⤊ 0⤋
Bob can wash 1/6 of a car in 1 minute. Bill can wash 1/8 of a car per minute.
Therefore, they can wash 1/6 + 1/8 = 4/24 + 3/24 = 7/24 of a car per minute.
1 minute = 7/24 of a car washed.
1 car washed = 24/7 or ~3.43 minutes or ~ 3 minutes 26 seconds.
2007-09-26 21:50:16 · answer #3 · answered by lhvinny 7 · 2⤊ 0⤋
Bob whash one car with 6 minutes and
Bill wash one car with 8 minutes
So when both washing same car then the time need to wash car will be 3 minutes approxmatly because
Bob will cover side of car and bill well cover the other side then
8 - 6= 3
2007-09-26 22:06:55 · answer #4 · answered by Rayan Ghazi Ahmed 4 · 0⤊ 0⤋
I got 3 min, 26 secs.
The way I did this was to use ratios to compare Bob and Bill's washing rates.
This is an inverse proportion problem,
so the more people washing, the shorter the time.
I first equate:
1 Bill (8min / 1 car) = 1 Bob (6 min / 1 car)
1 Bob = (8/6) * 1 Bill
Bob = 1.33 Bill
1 Bill + 1.33 Bill = 2.33 Bill
If it takes 8 min for 1 Bill to wash 1 car,
then how many mins does it take for 2.33 Bills to wash 1 car?
1 Bill (8 min / car) = 2.33 Bill (x min / car)
x = 8 / 2.33 = 3.4334796395 or 3 min and 26 secs (round up)
2007-09-26 21:57:55 · answer #5 · answered by Hiro 3 · 0⤊ 0⤋
4 minutes because since they are washing a car together they each do half and since Bob can wash a car in 6 minutes and Bill can wash a car in 8 minutes you half each their minutes. So Bob will take 3 minutes and Bill will take 4 minutes and Bob would be finished before Bill. Bill will wash the car for another minute after Bob is done and thus washing it together they'll take 4 minutes. Am I correct?
MISTAKE!!!
Let me try again...
I get it now...
Bill and Bob together will take 14 minutes to wash 2 cars then they will take... 7 to wash one? wait what?
2007-09-26 21:50:07 · answer #6 · answered by Evan S 2 · 0⤊ 1⤋
bob can wash a car in 6 min
in 1 min, he can wash 1/6 car
bill can wash a car in 8 min
in 1 min, he can wash 1/8 car
bob and bill in 1 min can wash 1/6 + 1/8 car= 7/24 car
So, they can wash 1 car in 24/7 minutes= 3.42 min
The answer is 3.42 minutes/car.
2007-09-26 21:55:12 · answer #7 · answered by XuraJ 2 · 0⤊ 0⤋
here is the formula for it:
T/6 x T/8 = (the common denominator of the #'s)
T/6 x T/8 = 24
now do the rest of the problem!
2007-09-26 21:50:54 · answer #8 · answered by Nmenna (men-uh) gosh darnit..... 3 · 0⤊ 1⤋
If the answer is not 7 ... then I will have to go with 14
2007-09-26 21:47:20 · answer #9 · answered by Nurse KeVo 5 · 0⤊ 1⤋
I think it would be 5 minutes
2007-09-26 21:46:15 · answer #10 · answered by Queen Liz 1 · 0⤊ 0⤋