Question 978681
jessica and cynthia work in a pet shop.
 it takes jessica 6 hours to groom all the pets but cynthia needs 8 hours to groom them.
 if jessica starts to groom 1 hour before cynthia joins, how long will it take them to finish?
:
let t = time it takes them to finish (C's working time)
then
t+1 = J's working time
let 1 = completed job (all pets groomed)
:
A shared work equation, each does a fraction of the job, the two fractions add up to 1
{{{((t+1))/6}}} + {{{t/8}}} = 1
Multiply by the least common multiple of 6 and 8, 24. cancel the denominators
4(t+1) + 3t = 24
4t + 4 + 3t = 24
4t + 3t = 24 - 4
7t = 20
t = 20/7
t = 2{{{6/7}}} hrs, which is: 2 + {{{6/7}}}*60 = 2 hrs 51.43 min to finish the job