721. Yalmaz can cover a distance of 400 metres in 2 minutes. Rayan can cover 1 km in 300 seconds. Find the ratio of their speeds.
Rayan’s speed = 1000/300 = 3.33 m/s
Hence Ratio = 1:1
722. If the ratio of the speeds of A and B to cover a distance of 200 m is 3:4, then the ratio of the time taken to cover the same distance is________?
If the ratio of the speeds of two objects is a:b, then the time taken by them to cover the same distance is
b:a Hence, the answer is 4:3
723. A car can travel 360km with a ¾ full tank. How many km can it travel with a 2/3 full tank?
With a full tank, it can travel
360*4/3 = 480 km With 2/3 full tank, it can travel
480*2/3 = 320 km
724. A boats man can row in still water at speed of 7 km/hr. It takes 6 hours more to travel the same distance in upstream than in downstream if the speed of the river is 3 km/hr. what is the distance between the two destinations?
A. 20 km
B. 40 km
C. 30 km
D. 10 km
x = 7 km/hr ; y = 3 km/hr
Ds = 10 km/hr ; Us = 4 km/hr
Distance (d) is same. Therefore, if time taken for downstream is t hours, the time for upstream is (t + 6) hours.
10*t = 4*(t + 6)
6t = 24 ; t = 4 hours
d = 10*4 = 40 km
725. If Afnan drives at 4/5th of his usual speed to his office, he is 6 minutes late. What is his usual time to reach his office?
Let t be his usual time to reach his office and v be his usual speed.
v = d/t ……….(d is the distance Afnan travels while going to his office)
vt = d
At v1 = 4v/5 ; t1 = t + 6
4v/5 = d/(t + 6)
4v/5* (t + 6) = d
4v/5* (t + 6) = vt
On solving we get,
t = 24 minutes
726. Two boys starts from the same place walking at the rate of 5 kmph and 5.5 kmph respectively in the same direction. What time will they take to be 8.5 km apart?
A. 17 hr
B. 14 hr
C. 12 hr
D. 19 hr
Relative speed = 5.5 – 5 = .5 kmph (because they walk in the same direction)
distance = 8.5 km
time = distance/speed=8.5/.5=17 hr
727. A cyclist covers a certain distance in 50 minutes at a speed of 24 kmph. To cover the same distance in 40 minutes, he should travel at a speed of__________?
A. 30 kmph
B. 27 kmph
C. 25 kmph
D. 20 kmph
Distance = 24*50/60 = 20 km New Speed = 20/(40/60)) = 30 kmph
728. Excluding stoppages, the average speed of a bus is 54 kmph and including stoppages, it is 45 kmph. For how many minutes does the bus stop per hour?
Due to stoppages, the bus travels only 45 kms in an hour (9 kms less). To cover a distance of 9 km at a speed of 54 kmph, time taken
= 9/54 = 1/6 hrs = 10 mins.
729. If a boat is rowed downstream for 50 km in 5 hours and upstream for 24 km in 6 hours, what is the speed of the boat and the river?
A. (7 , 3) km/hr
B. (6 , 4) km/hr
C. (10 , 4) km/hr
D. None of these
If x: speed of boats man in still water
y: speed of the river
Downstream speed (Ds) = x + y
Upstream speed (Us) = x – y
x = (Ds + Us) / 2
y = (Ds – Us) / 2
In the above problem Ds = 10 ; Us = 4
x = (10 + 4) / 2 = 14/2 = 7 km/hr
y = (10 – 4)/2 = 6/2 = 3 km/hr
730. Taimoor left for his school at 6 am by foot and walked at the rate of 2 kmph. After reaching his school he found it was closed and immediately turned back and started walking back to his home at 3 kmph. If he reached his home at 9 am, find the distance between his school and his home.
A. 2.5 km
B. 7.2 km
C. 7 km
D. 3.6 km
Average speed of Taimoor = (2*2*3)/(2 + 3) = 2.4 km/hr
If d is he distance between the school and Taimoor’s home, then total distance walked by Taimoor = 2d, and the total time taken is 3 hours
2.4 = 2d/3
7.2 = 2d
d = 3.6 km