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## Topic review (newest first)

mathsyperson
2005-07-30 02:18:52

Zach and MathsIsFun both already said that it was 6 hours.

raeann
2005-07-29 23:54:42

#### Hamster wrote:

Paula can clan the room in 3 hours.  Paula and Maria can clean it in 2 hours.  How long would it take Maria working alone to clean the room.

Thanks.

What is the answer?

Vulcan
2005-05-19 22:59:20

i cant be bothered working it out!
thanks for doing it for me!

MathsIsFun
2005-05-19 07:35:22

Let's look at how much they can do per hour (their "cleaning-up rate")

Paula is be able to clean 1/3rd of the room per hour. (1/3rd of a room times 3 hours = 1 room)

Paula and Maria together can clean 1/2 a room per hour.

So Maria's contribution is to speed things up from 1/3rd per hour to 1/2 per hour.

Let's calculate how much of an increase that is: 1/2 - 1/3 = 3/6 - 2/6 = (3-2)/6 = 1/6

So Maria is only really cleaning 1/6th of the room per hour.

So on her own it would be 6 hours.

(Maria is either very thorough at cleaning, or her heart isn't in it.)

Zach
2005-05-19 00:43:54

6 hours if it's dirty again in exactly the same way.

Something awefully strange is going on.

Hamster
2005-05-18 23:53:10

Paula can clan the room in 3 hours.  Paula and Maria can clean it in 2 hours.  How long would it take Maria working alone to clean the room.

Thanks.

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