Maths
2011-01-06 7:41 pm
John can finish a job alone in h hours while Peter can finish it alone in (h+3)hours, if they work together they can finish the job in two hours, find the value of h.
回答 (4)
2011-01-07 1:15 am
✔ 最佳答案
The equation should be like this2[1/h+1/(h+3)]=1
2(h+h+3)=h(h+3)
4h+6=h^2+3h
h^2-h-6=0
(h-3)(h+2)=0
h=3 or h=-2 (rejected)
The value of h is 3
2011-01-06 11:38 pm
I believe you can't simply add time or subtract time in this case, speed or the number of man-hours should be counted instead.
John speed = John/hr or 1/h (man per hour)
Peter speed = 1/(h+3) (man per hour)
adding speed,
1/h + 1/(h=3) = 2man per 2 hrs=1
1/h + 1/(h+3) =1
try solving this one and see if it's right?
kinda lazy...
lol
John speed = John/hr or 1/h (man per hour)
Peter speed = 1/(h+3) (man per hour)
adding speed,
1/h + 1/(h=3) = 2man per 2 hrs=1
1/h + 1/(h+3) =1
try solving this one and see if it's right?
kinda lazy...
lol
2011-01-06 8:47 pm
<h=3 >這是書中的標準答案, 只是不知如何列式 。
2011-01-06 8:28 pm
h + (h +3) = 2 X 2
2h + 3 = 4
2h = 4 - 3
2h = 1
h = 1/2 hr
therefore Peter finish job = 1/2 hour and John finish job = 3.5 hours
2h + 3 = 4
2h = 4 - 3
2h = 1
h = 1/2 hr
therefore Peter finish job = 1/2 hour and John finish job = 3.5 hours
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