A plane travels in the shape of equilateral triangle have sped of 20km/hr, 40km/hr and 60km/hr. Find the average speed of the palne.  Choices:
A) 42.73 km/h  B) 52.73 km/h  C) 32.73 km/h  D) 62.73 km/h  E) 72.73 km/h
average speed = total distance/total time taken   =(d+d+d)/[(d/20)+(d/40)+(d/60)] where d= side of eq. triangle   =3d/d[1/20 + 1/40 + 1/60]   =3*20*40*60/[20*40+40*60+20*60]   = 360/11 km/h   = 32.73 km/h   ANSWER:32.73 km/h
<result>C</result>
A plane travels in the shape of equilateral triangle have sped of 20km/hr, 40km/hr and 60km/hr. Find the average speed of the palne.