TIME AND DISTANCE IMPORTANT CONCEPT

Time and Distance - Important Formula

·          

1.    Speed, Time and Distance:

Speed =		Distance		,	Time =		Distance		,	Distance = (Speed x Time).
		Time					Speed

2.    km/hr to m/sec conversion:

x km/hr =		x x	5		m/sec.
			18

3.    m/sec to km/hr conversion:

x m/sec =		x x	18		km/hr.
			5

4.    If the ratio of the speeds of A and B is a : b, then the ratio of the

the times taken by then to cover the same distance is	1	:	1	or b : a.
	a		b

5.    Suppose a man covers a certain distance at x km/hr and an equal distance at y km/hr. Then,

the average speed during the whole journey is		2xy		km/hr.
		x + y
Q1:- If a person walks at 14 km/hr instead of 10 km/hr, he would have walked 20 km more. The actual distance travelled by him is:
A. 50 km B. 56 km C. 70 km D. 80 km Explanation: Let the actual distance traveled be x km. Then, x = x + 20 10 14 14x = 10x + 200 4x = 200 x = 50 km.
Q2-A train can travel 50% faster than a car. Both start from point A at the same time and reach point B 75 kms away from A at the same time. On the way, however, the train lost about 12.5 minutes while stopping at the stations. The speed of the car is:
A. 100 kmph B. 110 kmph C. 120 kmph D. 130 kmph Explanation: Let speed of the car be x kmph. Then, speed of the train = 150 x =  3 x Kmph. 100 2 75 - 75 = 125 x (3/2)x 10 x 60 75 - 50 = 5 x x 24 x = 25 x 24 = 120 kmph. 5
Q3- In a flight of 600 km, an aircraft was slowed down due to bad weather. Its average speed for the trip was reduced by 200 km/hr and the time of flight increased by 30 minutes. The duration of the flight is:
A. 1 hour B. 2 hours C. 3 hours D. 4 hours Explanation: Let the duration of the flight be x hours. Then, 600 - 600 = 200 x x + (1/2) 600 - 1200 = 200 x 2x + 1  x(2x + 1) = 3  2x2 + x - 3 = 0  (2x + 3)(x - 1) = 0  x = 1 hr.                [neglecting the -ve value of x]