if aaron can do a job in 8 days and ben can do the same job in 12 days how long does it take in hours for the two men working?
if aaron can do a job in 8 days and ben can do the same job in 12 days how long does it take in hours for the two men working together to complete the same job?
回答 (8)
AARON alone = 8 days
AARON ALONE in 1 DAY = 1/8 of the work
BEN ALONE in 1 DAY = 1/12 of the work
TOGETHER IN 1 DAY = 1/8+1/12 = 3/24+ 2/24 = 5/24 of the work
TOGETHER they will finish the work in 24/5 days OR 4.8 days ANSWER
1/8 + 1/12 = 1/x 3/24 + 2/24 = 5/24 = 1/x x=24/5=4.8 days
Let the work is as big as W=24A.
Then Aaron can do as much as W/8 = 3A daily while Ben can do W/12 = 2A. They can do 3A+2A=5A together.
So the time needed is (24A)/(5A) = 4.8 days
{Why we have taken 24A? Because of it is the LCM for 8, 12. You can use 8*12=96 instead.}
First use the standard formula, which is the
product of the two times divided by the sum.
So we get 96/20 = 4.8 . . . days, which equates
to 115.2 hours
If aaron can do a job in 8 days and ben can do the same job in 12 days how long does it take in hours for the two men working?
Aaron can do the job in 8 days ----> in 1 day, Aaron does 1/8 of job
Ben can do the job in 12 days ----> in 1 day, Ben does 1/12 of job
Working together, in 1 day the can do 1/8 + 1/12 = 5/24 of job
So together, they work at a rate of (5/24) job/day
1 job / (5/24 job/day) = 24/5 days.
Now the question is not clear what they mean by "day"
It's ridiculous to think either man can work 8 or 12 full 24-hour days non-stop. And using a 24-hour day to measure a job that is strung out over several 8 or 10 hour days doesn't make much sense.
Because of this, I'm not too sure how to answer this question.
But assuming a 24-hour work day (!), it would take them:
24/5 days * 24 hours/day = 115.2 hours
The equation I use is:
work = rate * time
We can find the rates of the two people using "1" as work (since it's the same job):
w = rt
1 = r * 8 and 1 = r * 12
r = 1/8 and r = 1/12
When both are working together, the rates are added:
1/8 + 1/12
3/24 + 2/24
5/24
So how long does it take when both are working together:
w = rt
1 = (5/24)t
t = 24/5 days (4.8 days)
To get it in terms of hours, multiply by 24:
576/5 hours (115.2 hours)
t/8+t/12=1
(3t+2t)/24=1
5t=24
t=24/5 d
t=4 days, 19 hours, 12 minutes
收錄日期: 2021-04-21 17:38:33
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