kiranck007 wrote:
Car X is 40 miles west of Car Y. Both cars are traveling east, and Car X is going 50% faster than Car Y. If both cars travel at a constant rate and it takes Car X 2 hours and 40 minutes to catch up to Car Y, how fast is Car Y going?
A. 20 miles per hour
B. 25 miles per hour
C. 30 miles per hour
D. 35 miles per hour
E. 40 miles per hour
Let speed of Y = V ,
speed of X = 1.5 V,
relative speed of X wrt Y (catch up speed of X) = 0.5V.
Now catch up speed = (distance between X and Y)/time.
0.5 V = 40 miles / (8/3 hour),
so V = 30 miles/hr.
However, what I don't understand is that the distance traveled by Car Y while Car X is catching up is not factored into the problem. Could someone clarify if my concern is valid, if not then reason.
Thanks,
Kiran
Using ratio approach to solve this problem
It's given that speed of X is 50% more than speed of Y---------> Speed of X =3/2 * Speed of Y
We can take speed of X=3k and Speed of Y=2K (I'm using K because I don't know the actual quantity)
X will cover 40 miles in 2 hours 40 minutes which means that the difference between X and Y of 40 miles is covered by X in 2 hours 40 minutes
Difference of X and Y covered by X (speed)= (40)/(8/3)= (40*3)/8 = 15 miles every hour-----------> Equation 1
Difference of X and Y = 3k-2k = K ---------------> Equation 2
Equating both of them we get
k=15 miles per hour.
Speed of Y= 2K = 2*15 mph= 30 miles per hour
Speed of X= 3*15 mph= 45 miles per hour.