Bill drives from city A to city B. After two hours of driving he noticed that he covered 80 km and calculated that, if he continued driving at the same speed, he would end up been 15 minutes late. So he increased his speed by 10 km/hr and he arrived at city B 36 minutes earlier than he planned.
Find the distance between cities A and B.  Answers:  A) 132 km  B) 250 km  C) 390 km  D) 440 km  E) 578 km
Let x be the distance between A and B. Since Bill covered 80 km in 2 hours, his speed was V=80/2= 
<gadget id="calculator">80/2</gadget>
<output>40</output>
40 km/hr.   If he continued at the same speed he would be 15 minutes late, i.e. the planned time on the road is x/40−15/60x hr. The rest of the distance is (x−80)) km. V=40+10= 
<gadget id="calculator">40+10</gadget>
<output>50</output>
50 km/hr.   So, he covered the distance between A and B in 2+x−80/50 hr, and it was 36 min less than planned. Therefore, the planned time was 2+x−80/50+36/60   When we equalize the expressions for the scheduled time, we get the equation:   x/40−15/60=2+x−80/50+36/60   x−10/40=100+x−80+30/50   x−10/4=x+50/5   5x−50=4x+200   x=250   So, the distance between cities A and B is 250 km.   correct answer is 250 km)250km
<result>B</result>
Bill drives from city A to city B. After two hours of driving he noticed that he covered 80 km and calculated that, if he continued driving at the same speed, he would end up been 15 minutes late. So he increased his speed by 10 km/hr and he arrived at city B 36 minutes earlier than he planned.
Find the distance between cities A and B.