SOLUTION: Jack usually mows his lawn in 7 hours. Marilyn can mow the same yard in 6 hours. How much time would it take for them to mow the lawn together? They could mow the lawn in ____

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Jack usually mows his lawn in 7 hours. Marilyn can mow the same yard in 6 hours. How much time would it take for them to mow the lawn together? They could mow the lawn in ____      Log On


   

Question 629092: Jack usually mows his lawn in 7 hours. Marilyn can mow the same yard in 6 hours. How much time would it take for them to mow the lawn together?
They could mow the lawn in _____ hours if they worked together. (simplify your answer)
Found 2 solutions by richwmiller, josmiceli:
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
x/7+x/6=1
6x/42+7x/42=1
13x=42
x=42/13
x=3.23 hrs or about 3 hrs 14 minutes

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of working
( 1 lawn / 7 hrs ) + ( 1 lawn / 6 hrs ) = ( 1 lawn / x hrs )
+1%2F7+%2B+1%2F6+=+1%2Fx+
Multiply both sides by +42x+
+6x+%2B+7x+=+42+
+13x+=+42+
+x+=+3+%2B+3%2F42+
+3%2F42+=+1%2F14+
+%281%2F14%29%2A60+=+4.2857+
+.2857%2A60+=+17.14+
They could mow the lawn in 3 hours 4 minutes and 17 seconds if they worked together.