Posted by **hiba** on Wednesday, November 30, 2011 at 6:13pm.

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 -
**hiba**, Wednesday, November 30, 2011 at 7:28pm
plz answer ....plz

- 3 grade math -
**Reiny**, Wednesday, November 30, 2011 at 7:55pm
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??)

- 3 grade math -
**hiba**, Wednesday, November 30, 2011 at 8:05pm
thank you so much .........

- 3 grade math -
**peter**, Sunday, February 5, 2012 at 7:36pm
12+6=18

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