A bus travels first one-fourth of the distance with a speed of 9 km/hr, next one fourth of the distance with 15 km/hr, third one-fourth distance with a speed of 20 km/hr and last one fourth with 30 km/hr. The average speed of the car for the whole journey is:  Options:
A) 19.09 km/hr  B) 29.09 km/hr  C) 39.09 km/hr  D) 49.09 km/hr  E) None of these
Explanation :   Let whole distance traveled be x   and average speed of the car be y   =&gt; (x/4)/10+(x/4)/20+(x/4)/30+(x/4)/40=x/y   =&gt; 1/10+1/20+1/30+x/40=4/y   =&gt; (24+12+4+3)/240=4/y   =&gt; 33/240=4/y   =&gt; y=29.09   Answer : 29.09 km/hr
<result>B</result>
A bus travels first one-fourth of the distance with a speed of 9 km/hr, next one fourth of the distance with 15 km/hr, third one-fourth distance with a speed of 20 km/hr and last one fourth with 30 km/hr. The average speed of the car for the whole journey is: