Question 221073
hannah can paint a room in 8hrs. Miley can paint it in 10hrs. working together, how many hrs would it take them to paint the room?
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Hannah does 1/8 room per hour.
Miley does 1/10 per hour.
Together, they do 1/8 + 1/10 per hour = 9/40 room per hour.
9/40 room/hour --> 40/9  hours/room
40/9 hours = ~ 4.44 hours
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There's a shortcut, product/sum
8*10/(8+10) = 80/18
= 40/9