Question 1097855
Bob: in 4 hours 1 fence, in 1 hour 1/4 fence
Sarah: 2.5 hrs to paint the fence, in 1 hour 1/2.5
1/4+1/2.5 = 5/20+8/20 = 13/20
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Ok, now let's call the time it will take them together t:
They will do 1 fence in t time: 1/t. Flip the equation and you get:
1/t = t/1 = 20/13 = 1 hour and 7/13 minutes = or 1 hour and 32.31 minutes or 1 hour 32 minutes and 19 seconds