SOLUTION: Suppose you are at a river resort and rent a motor boat for 5 hours starting at 7 A.M. You are told that the boat will travel at 8 miles per hour upstream and 12 miles per hour dow

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: Suppose you are at a river resort and rent a motor boat for 5 hours starting at 7 A.M. You are told that the boat will travel at 8 miles per hour upstream and 12 miles per hour dow      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 799445: Suppose you are at a river resort and rent a motor boat for 5 hours starting at 7 A.M. You are told that the boat will travel at 8 miles per hour upstream and 12 miles per hour downstream. You decide that you would like to go as far up the river as you can and still be back at noon. At what time should you turn back, and how far from the resort will you be at that time?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +t+ = time for boat to go upstream
+5+-+t+ = time to go downstream
--------------
Equation for going upstream:
+d+=+8t+
Equation for going downstream:
+d+=+12%2A%28+5+-+t+%29+
-------------------
By substitution:
+8t+=+12%2A%28+5+-+t+%29+
+8t+=+60+-+12t+
+20t+=+60+
+t+=+3+
---------
You should turn back in 3 hrs
---------
+d+=+8t+
+d+=+8%2A3+
+d+=+24+
You'll be 24 miles from the resort
-------------
check:
+d+=+12%2A%28+5+-+3+%29+
+d+=+12%2A2+
+d+=+24+
OK