How long would it take them to build the fence if they work together?
2007-12-01 01:56:10 · 7 answers · asked by jes 1 in Science & Mathematics ➔ Mathematics
Let length of fence = L metres
______________Jay_____Jen
time (hours)____ 5_______3
Rate of work ___L/5_____L/3
(m / h)
In 1 hour they build a length of:-
L / 5 + L / 3
3L / 15 + 5L / 15
8L / 15 m
Rate of work (R) = (8L / 15) m / h
Time = L / (8L / 15) h
Time = 15 / 8 h
Time = 1 7/8 h
2007-12-03 06:09:06 · answer #1 · answered by Como 7 · 1⤊ 1⤋
Jay builds 1/5 in one hour
Jen builds 1/3 in one hour
Working together they build 1/5+1/3 =8/15 of the fence in one hour
So the would need 15/8 hours to finish the fence =1h52min30seg
2007-12-01 10:07:17 · answer #2 · answered by santmann2002 7 · 1⤊ 1⤋
1/5 + 1/3 = 8/15
that is 15/8 hours to complete the fence = 1.875 hours
2007-12-01 10:00:50 · answer #3 · answered by hemant_gome 2 · 1⤊ 1⤋
1) can not say.
2) Let X be the quantitey of work.
jay can do X job in 5 hours. so in one hr jay can do X/5 work.
jen can do in one hour X/3 job.
If they work to gether they can do in one hour X/5 +X/3 work.
In one hour they can do 8X/15 work.
So X work they can do to gether in 15/8 hours.
They can build the fence together in 15/8 hours.
2007-12-01 14:11:13 · answer #4 · answered by Sasi Kumar 4 · 0⤊ 1⤋
1.875 hours
Jay can do it in 5 hours, so he can do 1/5 of the job in one hour.
Jen can do it in 3 hours, so she can do 1/3 of the job in one hour
the common denominator is 15 so 5/15 + 3/15 = how much will be done together in one hour...which is 8/15
15 / 8 = 1.875
2007-12-01 10:06:37 · answer #5 · answered by Rich 7 · 1⤊ 1⤋
8/15 hours
2007-12-01 12:32:59 · answer #6 · answered by Kenneth Koh 5 · 0⤊ 1⤋
pretty sure its (5*3) / (5+3) = 15/8 = 1.875 hours
i saw it in a movie a while ago and the answer makes sense
2007-12-01 10:01:45 · answer #7 · answered by Anonymous · 2⤊ 1⤋