Bunuel wrote:
A man travelled from one city to another. What is the distance between the two cities?
(1) He travelled the first 1/4 of his distance at a uniform speed of 15 miles per hour. Thereafter, he increased his speed to 20 miles per hour.
(2) The time for which he travelled at 20 miles per hour was 5 hours greater than the time for which he travelled at 15 miles per hour.
Let the total distance be D and total time taken be t
(1) gives us
t1 = (x/4)/15
t2 = (3x/4)/20
And we know t1 + t2 = t
but two variables and one equation
Not sufficient
(2) gives us t2 = 5 + t1
Alone not sufficient as we don't know the individual time
Say if t1 was 1 hr then distance would be 135 miles
if t1 is 2 hr then distance would be 170 miles
On combining we can solve for x
(3x/4)/20 = 5 + (x/4)/15
Hence C
_________________
We must try to achieve the best within us
Thanks
Luckisnoexcuse