A man rides at the rate of 20km/hr. But stops 20minutes to change horses at the end of every 30th kilometer. How long will he take to go a distance of 120 kilometers?  Options.
A) 5hr
B) 6hr 30min
C) 8hr 10min
D) 7hr
E) 9hr
speed of man = 20km/hr   number of rests = (120/30)-1= 
<gadget id="calculator">(120/30)-1</gadget>
<output>3</output>
3   time taken for the man= (120/20)+3*(20/60)= 
<gadget id="calculator">(120/20)+3*(20/60)</gadget>
<output>7</output>
7 hr   Answer is 7hr
<result>D</result>
A man rides at the rate of 20km/hr. But stops 20minutes to change horses at the end of every 30th kilometer. How long will he take to go a distance of 120 kilometers?