TOM traveled the entire 60 miles trip. If he did the first 12 miles of at a constant rate 24 miles per hour and the remaining trip of at a constant rate 48 miles per hour, what is the his average speed, in miles per hour? Choose the correct option.
A) 20mph B) 24mph C) 30mph D) 40mph E) 42mph
avg speed = total distance/ total time = (d1+d2)/(t1+t2) = (12+48) / ((12/24)+(48/48)) = 60*2/3= 
<gadget id="calculator">60*2/3</gadget>
<output>40</output>
40mph   40mph
<result>D</result>
TOM traveled the entire 60 miles trip. If he did the first 12 miles of at a constant rate 24 miles per hour and the remaining trip of at a constant rate 48 miles per hour, what is the his average speed, in miles per hour?