SAT Questions

fenchurchthesane says:

Yes. Fences = rate x time. Pat’s fences = pat’s rate x pat’s time, so 1 = pat’s rate x 2, so pat’s rate = 1/2 fence per hour. Jill’s fences = jill’s rate x jill’s time, so 1 = jill’s rate x 3, so jill’s rate = 1/3 fence per hour. Combining the rates, you get 1/2 + 1/3 = 5/6 fence per hour. 1 fence = 5/6 fences per hour x combined time, which is 6/5, which is 1 and 1/5 hour, which is 1 hour and 12 minutes.
There are other ways to do this but I took the dimensional analysis route.

Rec says:

pat paints a fence in 2 hrs, then in 1hr he can paint 1/2 of the fence. Samething with Jill, in 1hr, she can paint 1/3 of the fence.

Let t be the time it takes them to paint the fence together

(1/2)t + (1/3)t = 1
(5/6)t = 1
t = 1.2 hr or 1hr and 12min

you are correct!

starwhitedwarf says:

It will take them 1.2 hours to paint the fence together, or 1 hr 12 minutes.
Yes you are right.

sweet n simple says:

work done by pat in 1 hr = 1/2
work done by jill in 1 hr = 1/3

if they do together then in 1 hour they do
1/2+1/3 = 5/6 of the work
now
5/6 work is done in 1 hour
so 6/6 =1 work is done in 6/5 * 1=6/5 hours
=1.2 hours

dbondocoy@yahoo.com says:

work finished in one hour

x = 1 work

1/2 x+ 1/3x = 5/6X

so they can do 5/6 of the job in hour

5/6 of X per hour

to finished the job

t = X/ rate
t = x/(5/6x)
t = 6/5 hour

1hr 12 min