geraldo and luisa hernandez operate a small laundry. luisa, working alone, can clean a day's laundry in 9 hrs. geraldo can clean a day's laundry in 8 hrs. how long would it take them if they work together?
2007-12-10 21:57:36 · 4 answers · asked by gca18 1 in Science & Mathematics ➔ Mathematics
Let no. of articles = X
Geraldo`s rate of work = X/8 articles / h
Luisa`s rate of work = X/9 articles / h
Working together
X/9 + X/8 = 8X/72 + 9X/72 = 17X / 72 articles / h
Time = Work / rate of work
Time = X / (17X / 72) hours
Time = 72/17 hours
Time = 4 4/17 hours
Approx. 4 h 14 min (to nearest minute)
2007-12-10 22:12:10 · answer #1 · answered by Como 7 · 1⤊ 0⤋
speed of geraldo is 1job/8hrs
speedof luisa is 1job/9hours
total speed if they work together is 1/8+1/9=17/72 job/hour
1 job will take 72/17=4 4/17 hour
2007-12-10 22:01:21 · answer #2 · answered by someone else 7 · 0⤊ 0⤋
Luisa' s speed = 1/9
Geraldo's speed = 1/8
Their total speed = 1/9 + 1/8 = 9/72 + 8/72 = 17/72
Speed = work/ time
17/72 = 1/ t
17/72t = 1
t = 72/17
t = 4.23 hours
2007-12-10 22:10:07 · answer #3 · answered by detektibgapo 5 · 0⤊ 0⤋
together they will clean in time
= 9*8/(9 + 8) hrs
= 4 4/17 hrs
= 4 hrs 14 min 7 sec
2007-12-10 23:07:16 · answer #4 · answered by sv 7 · 0⤊ 1⤋