If A&B work together they will finish the job in 2 hours and 48 minutes. If they work independently; A will finish the job 4 hours and 12 minutes before B. The challenge is to find both their individual rate/speed for finishing the job if they work independently. Just to clarify (my English might a little un-clear), the A will do the job in X hours if he works alone; and B will finish the job in Y hours if he does it only by himself. ^^

Cheers & kudo for anyone who can solve this problem (and of course explain to me =)

Here's how to think it through - use the analogy of distance = rate time time. Suppose the job is to travel distance D. For worker A who takes time T_a to do his job his velocity is:

V_a = \frac D {T_a}


And for worker B you have


V_b = \frac D {T_b}


When they work together the time required is


T_{total} = \frac D {V_{total}}


Note that for all three equations D is a constant - it's the size of the job and is the same for both workers. When they work together their combined velocity is


V_{total} = V_a + V_b


So you have:


T_{total} \ = \ \frac D {V_{total}}\ =\ \frac D {V_a + V_b} \ = \ \frac D {\frac D {T_a} + \frac D {T_b}}\ = \ \frac 1 {\frac 1 {T_a} + \frac 1 {T_b}}


For your problem you've been given T_{total} and the value for T_a - T_b. So you can now solve for T_a and T_b. Post back and show us what you get for an answer.

its saying that if they work together they would finish faster if they work independently it would take them 2 hours more.so worker b you have Vb = D-T b
for a you have D-T a.so Va+Vb= . D v total