SOLUTION: a and b can cover certain distance in 2hours 30 minutes,a can cover the same in 3hours 30 minutes,in how many hours b alone take to cover the same distance

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Question 765115: a and b can cover certain distance in 2hours 30 minutes,a can cover the same in 3hours 30 minutes,in how many hours b alone take to cover the same distance
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
This is a rate problem. Add their rate of covering
distance to get their rate working together.
a's rate is ( 1 distance covered ) / ( 3.5 hrs )
a and b together rate: ( 1 distance covered ) / ( 2.5 hrs )
Let +t+ = hrs for b alone to cover distance
--------------------
+1%2F3.5+%2B+1%2Ft+=+1%2F2.5+
Multiply both sides by +2.5%2A3.5%2At+
+2.5t+%2B+2.5%2A3.5+=+3.5t+
+2.5t+%2B+8.75+=+3.5t+
+t+=+8.75+
b alone takes 8 hrs and 45 min to cover the same distance
----------------------
check:
+1%2F3.5+%2B+1%2Ft+=+1%2F2.5+
+1%2F3.5+%2B+1%2F8.75+=+1%2F2.5+
+.2857+%2B+.1143+=+.4+
+.4+=+.4+
OK