If A and B can fill a tank in 4 hours, A and C can fill the tank in 5 hours, and B fills twice as fast as C, how long does it take for C to fill the tank alone?
Fairly straightforward, but either the Invariants being slow, or we were all being polite and letting other people have a chance to figure it out...
So, I'm broswing around Sainsbury's, when I see they have large packs of Strongbow (18x440ml cans, normaly £14.99) reduced to half price. Seems like a good offer, but they also have 4-packs at £3.59 each with 500 nectar points if you buy two packs. In addition, these cans have x% extra free, making them a full pint. Question is, which of these offers is better value for money?
