<PRE><B>Question 729664</B>
    It takes Bob 4 hours longer to repair a car than it takes Ken. Working together, they can complete the job in 1.5 hours. How long would each of them take working alone.
.
Let x = time (hours) it takes ken to do job alone
then
x+4 = time it takes bob
.
1.5(1/(x+4) + 1/x) = 1
multiplying both sides by x(x+4):
1.5(x + x+4) = x(x+4)
1.5(2x+4) = x^2+4x
3x+6 = x^2+4x
6 = x^2+x
0 = x^2+x-6
0 = (x+3)(x-2)
x = {-3, 2}
throw out negative solution (extraneous) leaving:
x = 2 hours (Ken)
.
Bob:
x+4 = 2+4 = 6 hours</PRE>