Posted by Robert on Wednesday, March 7, 2012 at 12:30pm.
Mr Jones takes 4 hours to paint a fence.
Mark his son takes 6 hours to paint the same fence.
How long does it take for them both to paint the fence?

Maths  Steve, Wednesday, March 7, 2012 at 12:48pm
In one hour,
dad paints 1/4 fence
son paints 1/6 fence
together they paint 5/12 fence
so, they paint a whole fence in 12/5 hours, or 2 hrs 24 min 
Maths  Sydney, Wednesday, November 2, 2016 at 9:34pm
It takes them 10 hours to complete two fences, so to complete one together, it would take 5 hours