IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => IGCSE/ GCSE => Math => Topic started by: Ghost Of Highbury on May 18, 2009, 07:17:14 am

Title: Math question really stuck
Post by: Ghost Of Highbury on May 18, 2009, 07:17:14 am

heres d question : 2 pipes A and B can fill a tank in 36 hours and 45 hours respectively. If both pipes are opened simultaneously, how much time will be taken to fill the tank?

Title: Re: Math question really stuck
Post by: Ghost Of Highbury on May 18, 2009, 07:22:50 am

anyone dere..

nid404..plz help..!!

Title: Re: Math question really stuck
Post by: astarmathsandphysics on May 18, 2009, 07:24:20 am

I cant find this question where is it?

Title: Re: Math question really stuck
Post by: Ghost Of Highbury on May 18, 2009, 07:25:48 am

i got it from a practice book...

Title: Re: Math question really stuck
Post by: godfather93 on May 18, 2009, 07:26:23 am

there is no other hint?

Title: Re: Math question really stuck
Post by: O.T.13. on May 18, 2009, 07:26:49 am

i think this is average
just add them and divide them by two, can't think of anything else, and there aint that much numbers to work with

Title: Re: Math question really stuck
Post by: Ghost Of Highbury on May 18, 2009, 07:27:58 am

the answer is 20...don't know how they solved it,,,

Title: Re: Math question really stuck
Post by: astarmathsandphysics on May 18, 2009, 07:28:41 am

Quote from: eddie_adi619 on May 18, 2009, 07:17:14 am

heres d question : 2 pipes A and B can fill a tank in 36 hours and 45 hours respectively. If both pipes are opened simultaneously, how much time will be taken to fill the tank?

flow rate for 1 =f1 and for 2=f2  so 36f1=V and 45f2=V so f1=V/36 and f2=V/45 and total flow rate =f1+f2=V/36+V/45=81V/1620=V/20

so f=V/20 and 20f=V and time =20 hours

Title: Re: Math question really stuck
Post by: Ghost Of Highbury on May 18, 2009, 07:28:47 am

no more hints given,,,

Title: Re: Math question really stuck
Post by: Ghost Of Highbury on May 18, 2009, 07:29:52 am

okk..
thanks a lot astar..
really good explanation