Question 936037
average speed  = {{{ total distance / total time }}}
total time  =  1 hr +2 hr = 3 hrs
   distance traveled in first 1 hr   = speed * time
                                        =10*1
                                       =10 miles
distance traveled in next 2 hrs  =   25*2 
                                       =50 miles
total distance  = 10+50 = 60 miles
 average speed  ={{{ 60/3}}}
              = 20 miles /hr
 Result : Average  speed  =  20 miles /hr