Arjun leaves home everyday at 4 p.m to pick his son from school and returns home at 6 p.m. One day, the school was over at 4 p.m and the son started walking home from school. Arjun, unaware of this, starts from home as usual and meets his son on the way and returns home with him 15 minutes early. If the speed of Arjun is 30 km\hr, find the speed of his son. Pick one.
A) 15km/hr
B) 6 km/hr
C) 4.28 km/hr
D) 9 km/hr
E) 4.12 km/hr
Arjun leaves home everyday at 4 p.m to pick his son from school and returns home at 6 p.m. One day, the school was over at 4 p.m and the son started walking home from school. Arjun, unaware of this, starts from home as usual and meets his son on the way and returns home with him 15 minutes early. If the speed of Arjun is 30 km\hr, find the speed of his son.   The distance from home to school is 30 km. The round trip distance = 60 km. Because he returns home 15 minutes early, I thought it might be easier to break his trip up into 8 identical 15 minute blocks, each of which he traveled at 7.5 km/hour.   Because we are dealing with a round trip here, Arjun would have stopped 7.5 minutes short of the school. This means he traveled Distance=rate* time .5Km/hour*52.5 minutes or 26.25 KM. His son therefore traveled 3.75km/hour by the time he met his dad at 4:52.5. It took the son 52.5 minutes to travel 3.75 km. Because we are trying to find the son's rate per hour (i.e. 60 minutes) and we have his speed for 52.5 minutes it's best to convert to km/minute then multiply by 60 to get km/hour   3.75km/52.5 = .07 km/minute   .07km/minute*60 minutes = 4.28 km/hour.   Answer: C. 4.28 km/hr
<result>C</result>
Arjun leaves home everyday at 4 p.m to pick his son from school and returns home at 6 p.m. One day, the school was over at 4 p.m and the son started walking home from school. Arjun, unaware of this, starts from home as usual and meets his son on the way and returns home with him 15 minutes early. If the speed of Arjun is 30 km\hr, find the speed of his son.