Respuesta :

AL2006
-- Driving at 30 mph for 20 minutes (1/3 hour), you cover 10 miles.

-- Walking at 3 mph for 10 minutes  (1/6 hour), you cover 0.5 mile.

-- Average speed  =  (total distance covered) / (time to cover the distance) 

                                =        (10.5 miles) / ( 1/2 hour)

                                =            21 miles per hour. 
[tex]Formula = \ Average \ speed \ - \ (total \ distance \ covered) / [/tex] [tex] (time \ to \ cover \ the \ distance) [/tex]

       [tex]Divide [/tex]          [tex]=\ \textgreater \ (10.5 \ miles) / ( 1/2 \ hour)[/tex]

                                          [tex] =\ \textgreater \ 21 \ miles \ per \ hour. [/tex]