Posted by Tyler on .
A painter needs 3 days to paint the walls of a room. How long would it take him, working at the same rate, to paint a room that is twice as long, twice as wide, and twice as high as the original room?

Math 
drwls,
The area of all the walls scales with the square of the linear dimension, as they remain similar in shape but increase in size. Doubling all the linear dimensions multiplies tha total area by 4. Painting the enlarged room therefore takes 4 x 3 = 12 days.

Math 
Lramirez,
At an automotive repaire shop, 3.5 h of labour costs $311.50.
a) What is the labour charge a 5h job?
b) How could you check you answer?