1/3 of a certain journey is covered at the rate of 25km/hr,1/4 at the rate of 30 km/hr and the rest is 50 km/hr.the avg speed for the whole journey is :  Select:
A) 30 km/hr
B) 33 km/hr
C) 33 1/3 km/hr
D) 37 1/12 km/hr
E) 37 km/hr
let assume total distance will be 120km then   distance traveled at teh speed 25km/hr=1/3*120= 
<gadget id="calculator">1/3*120</gadget>
<output>40</output>
40km the time=40/25= 
<gadget id="calculator">40/25</gadget>
<output>8/5 = around 1.6</output>
1.6hrs   distance traveled at the speed 30km/hr=1/4*120= 
<gadget id="calculator">1/4*120</gadget>
<output>30</output>
30kmthe time is=30/30= 
<gadget id="calculator">30/30</gadget>
<output>1</output>
1 hr   then remaining distance is 120-40-30= 
<gadget id="calculator">120-40-30</gadget>
<output>50</output>
50km   the time taken to travel 50km=50/50= 
<gadget id="calculator">50/50</gadget>
<output>1</output>
1hr   so total time is=1.6+1+1= 
<gadget id="calculator">1.6+1+1</gadget>
<output>3.6</output>
3.6 hrs   so avg speed=120/3.6=33.33km/hr   ANSWER:33 1/3 km/hr
<result>C</result>
1/3 of a certain journey is covered at the rate of 25km/hr,1/4 at the rate of 30 km/hr and the rest is 50 km/hr.the avg speed for the whole journey is :