one bulldozer clearing land twice as fast as another, together they clear a large tract in 1 1/2 hours. how lo?
Let the smaller bulldozer clear it in x hours. 1/x + 1/2x = 1/1.5 The common denominator is 2x. 2/2x + 1/2x = 1/(3/2) (3/2 ) x = 2/3 x = 2/3 // 3/2 x = 2/3 * 2/3 x = 4/9 What does the answer for x represent? It has the units of hours over job. You need the inverse of those units. So the faster one uses 9/4 hours to do the job and the slower one needs 9/2 = 4.5 hours. The faster one does the job in 2.25 hours.
