SOLUTION: two pipes are used to pump a cement mixture out of a truck. the pipes work at the same rate. when pipe A works alone it can empty the truck in 45 minutes. when both pipes are used

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Question 1030837: two pipes are used to pump a cement mixture out of a truck. the pipes work at the same rate. when pipe A works alone it can empty the truck in 45 minutes. when both pipes are used together they empty the truck in 2/3 of the time that it takes pipe B to empty the truck it works alone. suppose pipe B takes x hours to empty the truck when it works alone. which equation can be used to find x?
Found 2 solutions by josmiceli, ikleyn:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Rate of emptying for pipe A:
[ 1 truck emptied ] / [ 3/4 hrs ]
Rate of emptying for pipe B:
[ 1 truck emptied ] / [ x hrs ]
Rate of emptying for both pipes together:
[ 1 truck emptied ] / [ (2/3)*x hrs ]
------------------------------------
Add rates for pipes A and B to get
rate for both pipes together:
+1%2F%28%283%2F4%29%29+%2B+1%2Fx+=+1%2F%28%282%2F3%29%2Ax%29+
+4%2F3+%2B+1%2Fx+=+3%2F%28+2x+%29+
Multiply both sides by +6x+
+8x+%2B+6+=+9+
+8x+=+3+
+x+=+3%2F8+
----------------
check answer:
+1%2F%283%2F4%29+%2B+1%2F%283%2F8%29+=+1%2F%281%2F4%29+
+4%2F3+%2B+8%2F3+=+4+
+12%2F3+=+4+
+4+=+4+
OK

Answer by ikleyn(52777) About Me  (Show Source):
You can put this solution on YOUR website!
.
Your condition is wrong.