SOLUTION: It is estimated that a bulldozer can prepare a certain site in 15.0 days and that a larger bulldozer can prepare the same site in 11.0 days. If we assume that they do not get in

Algebra ->  Rate-of-work-word-problems -> SOLUTION: It is estimated that a bulldozer can prepare a certain site in 15.0 days and that a larger bulldozer can prepare the same site in 11.0 days. If we assume that they do not get in       Log On


   

Question 1204765: It is estimated that a bulldozer can prepare a certain site in 15.0 days and that a
larger bulldozer can prepare the same site in 11.0 days. If we assume that they do
not get in each other’s way, how long will it take the two machines, working
together, to prepare the site?
Found 2 solutions by mananth, josgarithmetic:
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
It is estimated that a bulldozer can prepare a certain site in 15.0 and that a
larger bulldozer can prepare the same site in 11.0 days. If we assume that they do
not get in each other’s way, how long will it take the two machines, working
together, to prepare the site?

bulldozer can prepare a certain site in 15.0 days
So it prepares 1/15 of the site in 1 day
larger bulldozer can prepare the same site in 11.0 days.
So it prepares 1/11 of the site in 1 day
In one day both working together will prepare 1/15+1/11 of the site
1/11 + 1/15 = (15+11)/15*11 = 26 /165
They will take 165/26 days to complete the job 6.35 days (rounded off)



Answer by josgarithmetic(39630) About Me  (Show Source):
You can put this solution on YOUR website!
                   RATE          TIME            HOW MANY SITES DONE

bulldozer          1/15           15              1

largerbulldozer    1/11           11              1

combined          1%2F15%2B1%2F11

Their combined speed,11%2F%2811%2A15%29%2B15%2F%2811%2A15%29;

The reciprocal of that is how many days to do one site both these bulldozers together.