Well done, guys! I'm guessing you used some kind of calculator?
I'ma take Sputnik's as an example:
100/(100/8+100/6-100/4)=100/(100(3/24+4/24-6/24))=1/((3+4-6)/24)=24/(3+4-6)=24
This only proves 0.999...=1 :banana:
Eventhough you calculated it, I'm going to show you guys how I did.
V = volume, t = time
t(V/8+V/6-V/4)=V
where V/8, V/6 and V/4 just calculates how much volume/minute the different pipes can pour/drain.
Doing the equation should give you t = 24.
If someone has a brainteaser, post it. If not, I can post another one.
VG; You'd also get 24 minutes exact if you hadn't rounded off too early.