tauchmeister wrote:
I'm having problems with the following question to,
It is from and old set I have with me,
I have no idea from the source.
One hour before John started walking from P to
Q, a distance of 18 miles, Ann had started walking
along the same road from Q to P. Ann walked at a
constant speed of 3 miles per hour and John at 2
miles per hour. How many miles had Ann walked
when they met?
a) 6 miles
b) 8,4 miles
c) 9 miles
d) 9,6 miles
e) 12 miles
Official answer E
Thanks
This is again a relative speed question and I would suggest you to check out the links given in my previous post.
Ann walks from Q to P at a speed of 3 miles/hr for one hour. She covers 3 miles in 1 hour and now distance between John and Ann is 18 - 3 = 15 miles.
Ann walks at 3 mph and John at 2 mph so their relative speed is 3+2 = 5 mph.
They have to cover 15 miles so it will take them 15/5 = 3 hours to meet.
In 3 hrs, Ann would have covered 3 hrs * 3 miles per hour = 9 miles.
Adding this to the 3 miles she covered before John, Ann covered a total of 3 + 9 = 12 miles.
Answer (E)
Another Method:
You can also use ratios to say that Ann and John have 15 miles between them (after Ann covers 3 miles) and their speeds are in the ratio 3:2. So Ann will cover 3/5 of the distance i.e. (3/5)*15 = 9 miles.
This gives a total distance of 3 + 9 = 12 miles
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