SOLUTION: Sylvia ran for 15 minutes at a rate of 5 miles per hour and then walked for 15 minutes at a rate of 4 miles per hour. What was her average speed? How far did she go?

Algebra ->  Average -> SOLUTION: Sylvia ran for 15 minutes at a rate of 5 miles per hour and then walked for 15 minutes at a rate of 4 miles per hour. What was her average speed? How far did she go?      Log On


   

Question 972342: Sylvia ran for 15 minutes at a rate of 5 miles per hour and then walked for 15 minutes at a rate of 4 miles per hour. What was her average speed? How far did she go?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Average speed is always:
[ total distance traveled ] / [ total time spent traveling ]
Convert +15+ min to hrs:
+15%2F60+=+1%2F4+ hrs
---------------------
+d%5B1%5D+=+5%2A%281%2F4%29+
+df%5B1%5D+=+5%2F4+ mi
-------------------
+d%5B2%5D+=+4%2A%28+1%2F4+%29+
+d%5B2%5D+=+1+ mi
-------------------
+d%5B1%5D+%2B+d%5B2%5D+=+5%2F4+%2B+4%2F4+
+d%5B1%5D+%2B+d%5B2%5D+=+9%2F4+ mi
--------------------------
+t%5B1%5D+%2B+t%5B2%5D+=+1%2F4+%2B+1%2F4+
+t%5B1%5D+%2B+t%5B2%5D+=+1%2F2+ hr
----------------------
Average speed =
+%28+9%2F4+%29%2F+%28+1%2F2+%29+=+9%2F2+
+9%2F2+=+4.5+ mi/hr
The average speed is 4.5 mi/hr
+9%2F4+=+2.25+
She went 2.25 mi