Problems of the Day

Grade School problem in China, but probably for most of you will be middle school xD:

Pipe A can fill a pool in 2 hours, pipe B can fill it in 1 hour, if pipe C can fill it in x hours, and altogether the pool can be filled in 30 minutes, what is x?

omg china school system and education system is similar to Korea!! we also learn those kind of problems which is mostly about "x"

Isn't that just algebra

yeah

whatever XP

so anyone can solve it???

yes and no i knida know but kinda don't XD

Isn’t it 2

Correct

My solution:

Pipe A= 1/2 pool/hour

Pipe B= 1 pool/hour

Pipe C= y pool/hour

So in 30 minutes it's :

0.5*0.5+1*0.5+0.5y=1

And just solve y for how much pipe C have fill the pool for 1 hour

(1/4)+(1/2)+(1/2)y=1

3/4+(1/2)y=1

(1/2)y=1/4

y=1/2 pool/hour

Then just search x with velocity equation

x= 1 pool / 1/2 pool/hour

=1*2

=2 hour

Yes, and from that result we deduce that Pump A = Pump C => we choose the most cost-effective pump x2.