An experienced electrician can wire a room twice as fast as an apprentice electrician. Working together, the electricians can wire a room in 3 hour. How long would it take the apprentice working alone to wire a room?
Love this kind of problems! :) ~~~~~~~~~ Suppose that an experienced electrician can wire a room for x hours with productivity 1/x . Then an apprentice electrician can wire a room for 2x hours with productivity 1/(2x) . On the one hand their productivity is 1/3 , and on the other hand their productivity is (1/x + 1/(2x)) . Now we are ready to write equation 1/x + 1/(2x) = 1/3 LCD(x, 2x, 3) = 6x (6 + 3)/(6x) = 2x/(6x) ---> 9/(6x) = 2x/(6x) ---> 2x = 9 hours