Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#1 2005-05-18 01:53:10

Hamster
Member
Registered: 2005-05-18
Posts: 1

Help Solve Rate Question

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.

Offline

#2 2005-05-18 02:43:54

Zach
Member
Registered: 2005-03-23
Posts: 2,075

Re: Help Solve Rate Question

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

Something awefully strange is going on.

Last edited by Zach (2005-05-18 21:30:35)


Boy let me tell you what:
I bet you didn't know it, but I'm a fiddle player too.
And if you'd care to take a dare, I'll make a bet with you.

Offline

#3 2005-05-18 09:35:22

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,552

Re: Help Solve Rate Question

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.)


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

Offline

#4 2005-05-19 00:59:20

Vulcan
Member
Registered: 2005-04-23
Posts: 224

Re: Help Solve Rate Question

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


one day, i couldn't find my hat
then it occured to me that i didn't have one
so i didn't where it!!!

Offline

#5 2005-07-29 01:54:42

raeann
Member
Registered: 2005-07-29
Posts: 2

Re: Help Solve Rate Question

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?

Offline

#6 2005-07-29 04:18:52

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: Help Solve Rate Question

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


Why did the vector cross the road?
It wanted to be normal.

Offline

Board footer

Powered by FluxBB