simple question yet complicated for a newbie

[aakarim]

Hi everyone
i am a doctor preparing for my GMAT to get into a health Sector Management program. I have started studying maths after a very long time which mean of course , I happen to get stuck in very easy things as well....

like this question:

Simon paints the house in 2 hours, Sam paints it in 3 hours. If they both paint it togeter, how much time will it take to paint the house.


Could someone comment on how to solve such an easy question thats giving me nightmares...


Secondly there are so many books available all over the internet. COuld you specify some books that actually "explain" the answers instead of just simply putting them down.


thanks
Dr Arsalan

[moutar]

Simon paints 1/2 the house in one hour and Sam paints a 1/3 if the house in an hour. Therefore in one hour 5/6 of the house has been painted between them.

Then, it take 12 mins to paint 1/6 of the house
-> it take 1h 12 mins to paint the whole house.

[ssmiles08]

You can use the following formula:

1/x + 1/y = 1/t

x = the rate person A can paint the house (2 hours)
y = the rate person B can paint the house (3 hours)
t = time

1/2 + 1/3 = 1/t

1/t = 5/6; t = 6/5

So they paint it int 6/5 hour ==> convert that into minutes (6/5)*60 = 72 minutes = 1 hour and 12 minutes