Question 173571
You hav eto add their rates of working
In words:
(1 car repaired)/(T's time to repair) + (1 car repaired)/(J's time to repair)
= (1 car)/(combined times)
{{{1/7 + 1/8 = 1/x}}}
Multiply both sides by {{{56x}}}
{{{8x + 7x = 56}}}
{{{15x = 56}}}
{{{x = 3.73333}}}hrs
{{{.7333*60 = 44}}}
Working together, it takes them 3 hrs and 44 min
This problem assumes a lot, and it's a good mental excercise
imagining why this answer might be wrong
Would they get in eachother's way fixing the car?
Do they get along with eachother?
Do they have to share tools?
Can they actually help eachother so much that
the time is less than expected
On and on and on, but I gave you the "expected" answer