Question 195186
Kathrin and Tom together clean the garage in 3 hours. 
Separatly, it takes Tom one hour more then Kathrin.
 How long does it take the to clean the garage seperatly?
 Approximate to the nearest tenth of an hour.
;
Let t = time required for K to do the job alone
then
(t+1) = time for T to do the same job alone
:
let the completed job = 1
:
Each will do a fraction of the job; the two fractions add up to 1
:
{{{3/t}}} + {{{3/((t+1))}}} = 1
:
Multiply equation by t(t+1)
t(t+1)*{{{3/t}}} + t(t+1)*{{{3/((t+1))}}} = t(t+1)(1)
cancel out the denominators and you have:
3(t+1) + 3t = t(t+1)
:
3t + 3 + 3t = t^2 + t
:
6t + 3 = t^2 + t
arrange as a quadratic equation
0 = t^2 + t - 6t - 3
:
t^2 - 5t -3 = 0
Use the quadratic formula; a=1; b=-5; c=-3
:
Do math here:
{{{t = (-(-5) +- sqrt(-5^2 - 4 * 1 * -3 ))/(2*1) }}}
the positive solution:
t = 5.54 hrs, is K's time alone
and
6.54 = T's time alone