Moved - word problem

[robert mclaughlin]

word problem

jean can stack a pile of wood in 2 hrs, and sandy can do the same job in 4 hrs. how long will it take to do the job together? I am using the reciprocal method used for the total ohms for 2 dif ohm resistors in parallel. 10 ohm and 20 ohm, 1/10+1/20 =.15 1/.15 = 6.67 ohms, so my thinking is 1/240 (mins) + 1/120 =.0125 1/.0125= 80 mins will this work?

 

[Deleted member 4993]

jean can stack a pile of wood in 2 hrs, and sandy can do the same job in 4 hrs. how long will it take to do the job together? I am using the reciprocal method used for the total ohms for 2 dif ohm resistors in parallel. 10 ohm and 20 ohm, 1/10+1/20 =.15 1/.15 = 6.67 ohms, so my thinking is 1/240 (mins) + 1/120 =.0125 1/.0125= 80 mins will this work?

Yes...

What fraction of a pile can Jean put in 1 hr? 1/2

What fraction of a pile can Sandy put in 1 hr? 1/4

What fraction of a pile can (Jean+Sandy) put in 1 hr? 1/4 + 1/2 = 3/4

So working together, Jean and Sandy will take (4/3 hrs. = ) 80 minutes to stack a pile of woods.

 

[MarkFL]

I would approach this by considering that in 4 hours, working together they can stack 3 piles of wood. So in 4/3 hours they can stack 1 pile of wood. 4/3 hr = 80 min.