12:00 May 24, 2011 

I have hidden my answer "rules of three assignment". I amnot wasting my time any longer

11:42 May 24, 2011 

The Oxford dictionary does indeed define "rule of three" as "a method of finding a number in the same ratio to one given as exists between two others given", but I'm not sure that the term is widely understood. For what it's worth, I asked a 30-year-old with a first-class maths degree from Cambridge if he knew what a "rule of three" problem was and he had no idea. Googling "rule of three" produces references to a wide range of topics, often to do with including 3 main points in a talk or presentation.

10:26 May 24, 2011 

There is no need to agree with me. The reason you are agreeing with somedody else's answer is, however, ludicrous. When you went to school, there was no SMS, no page file and no Airbus 380.

05:25 May 24, 2011 

The answer to your question would be 20 days, because they are in each others way. - This problem is also not the same type as the examples stated by the asker.

23:00 May 23, 2011 

And I always knew these things as "algebra problems." Something like this:
"Say Frank can build a model airplane in 3 days, Jo can do it in 2, but Moe can only do it in 5 days. If they work together, they’ll build a model plane in:"
This falls into the SAT algebra section (among other problems).