SOLUTION: A dog ran at 30 km/hr for 40 minutes and then returned to the starting point at 20 km/hr.find it's average speed

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: A dog ran at 30 km/hr for 40 minutes and then returned to the starting point at 20 km/hr.find it's average speed       Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 1014218: A dog ran at 30 km/hr for 40 minutes and then returned to the starting point at 20 km/hr.find it's average speed
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Convert minutes to hrs
+40%2F60+=+2%2F3+ hrs
The one-way distance is:
+d+=+30%2A%282%2F3%29+=+20+ km
and, for the return to start:
+20+=+20%2At+
+t+=+1+ hr
-------------
Average speed is always
[ total distance ] / [ total time ]
+%28+20+%2B+20+%29+%2F+%28+2%2F3+%2B+1+%29+
+40%2F%28+5%2F3+%29+
+%283%2F5%29%2A40+=+24+
The average speed is 24 km/hr