Work done together problem

[Omid]

A can do a piece of work in 4 days and B in 6 days. How long will they require working together ?

Hint. 1/4 + 1/6 = 1/x


I just don't get them ( The problem and the hint).
Can you help me understand it ?

 

[.....]

one piece of work in four days plus one piece of work in six days equals one piece of work in x days

 

[Fredrik]

Question: Suppose A and B are eating potato chips from the same bag. It would take A 4 minutes to eat all the chips if B wasn't there. It would take B 6 minutes to eat all the chips if A wasn't there. How long will it take the two of them to finish that bag of chips?

Hint: In one minute, A eats 1/4 of the chips and B 1/6 of the chips, so 1/4+1/6 of the bag will be eaten each minute. If they keep eating for x minutes, they will have eaten (1/4+1/6)x of the bag. The bag will be empty when this equals 1, so all you have to do is to solve the equation (1/4+1/6)x=1.

 

[Omid]

Question: Suppose A and B are eating potato chips from the same bag. It would take A 4 minutes to eat all the chips if B wasn't there. It would take B 6 minutes to eat all the chips if A wasn't there. How long will it take the two of them to finish that bag of chips?

Hint: In one minute, A eats 1/4 of the chips and B 1/6 of the chips, so 1/4+1/6 of the bag will be eaten each minute. If they keep eating for x minutes, they will have eaten (1/4+1/6)x of the bag. The bag will be empty when this equals 1, so all you have to do is to solve the equation (1/4+1/6)x=1.

Thank you very very very very much.

 

[humanino]

Fredrik posted a very pedagogical hint :
Suppose A and B are eating potato chips from the same bag.
Doubtlessly students must pay more attention to potato chips than to abstract pieces of work.