SOLUTION: To get to work, you drive for 20 minutes at 30 mph, and walk 10 more minutes at 3 mph. What was your average speed? a) 16.5 mph b) 20 mph c) 21 mph d) 23 mph

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: To get to work, you drive for 20 minutes at 30 mph, and walk 10 more minutes at 3 mph. What was your average speed? a) 16.5 mph b) 20 mph c) 21 mph d) 23 mph       Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 602915: To get to work, you drive for 20 minutes at 30 mph, and walk 10 more minutes at 3 mph. What was your average speed?

a) 16.5 mph
b) 20 mph
c) 21 mph
d) 23 mph

Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

Note D = r*t   20min = 1/3 hr and 10min = 1/6 hr

(1/3hr)30mph + (1/6hr)3mph = 10.5 mi, the total distance traveled.

 total distance / total time = average speed = 10.5/(1/3 + 1/6) = 10.5/(2/6 + 1/6)

10.5mi/.5hr = 21mph