Hi, there. I'm happy to give my two cents on this one.
This is a cool question! Here's my analysis:
Ramesh leaves home at 5pm to pick up his daughter from school and returns home at 7 pm
So, the trip there takes an hour, and the trip home takes an hours.
The speed of Ramesh's car is 40km/hr
So, the school is 40 km away from home.
One day the school was over at 5pm and the daughter instead of waiting for her father started walking towards home. Ramesh as usual started from home and met his daughter on the way and returned home 12 minutes earlier.
So, instead of turning around at the school, Ramesh drove to some intermediate distance, where he met his daughter, and drove home from that place. Obviously, the trip to that place and from that place must have taken the same time, so he got to that place 6 minutes before 6 pm, in 54 minutes, and drove home from there in 54 minutes. 54/60 = 9/10 hour.
Therefore the distance to that place is:
D = RT = (40 km/hr)*(9/10 hr) = 36 km
The point where Ramesh met his daughter is 36 km away from home. This means, the daughter walked 4 km in that time.
The daughter walked 4 km in 9/10 hour. So
R = D/T = (4)/[9/10] = 40/9 km/hr
Answer =
A
Great question. Here's another practice question on speed:
https://gmat.magoosh.com/questions/5
When you submit your answer to this question, the next page will have the video explanation. At Magoosh, each of our 800+ GMAT practice questions have an accompanying video explanation. We are having a sale right now, ending later this week, so you will never find GMAT prep of this quality so cheap. It's an excellent time to check out Magoosh.
Let me know if you have any further questions.
Mike
