if a man cut grass in 6 hour , another man cut in 12 hour , how many hour ther were both spend if they cut grass toghter.

answer 9 hour or 4 hour

plz answer ....plz

rate of first man = 1/6 lawn/hr

rate of 2nd man = 1/12 lawn/hr
combined rate = 1/6 + 1/12 = 3/12 or 1/4 lawn/h

time takes when both cutting = 1/(1/4)
= 1 (4/1) = 4 hrs

(how can the combined work take 9 hours, if one guy alone can do it in 6 hrs??)

thank you so much .........

12+6=18

To find out how many hours they would spend if they cut the grass together, we need to calculate the time it would take for them to finish the job when working together.

We can solve this using the concept of rates. The rate at which the first man cuts grass is 1/6 of the job per hour (since he finishes the job in 6 hours). Similarly, the rate at which the second man cuts grass is 1/12 of the job per hour (since he finishes the job in 12 hours).

When they work together, their rates add up, so the combined rate is (1/6) + (1/12) = (2/12) + (1/12) = 3/12 = 1/4 of the job per hour.

To find out how long it would take for them to finish the job when working together, we can use the formula: Time = Job / Rate.

Since the job is to cut the grass completely (1 job), the time it would take for them to finish the job together is: Time = 1 / (1/4) = 4 hours.

Therefore, if the first man takes 6 hours to cut the grass alone, and the second man takes 12 hours to cut the grass alone, when they work together, they will finish cutting the grass in 4 hours.