TIME SPEED AND DISTANCE1. 1 Kmph = (5/18) m/s 2. 1 m/s = (18/5) Kmph 3. Speed(S) = Distance(d)/Time(t) 4. Average Speed = Total distance/Total Time = (d1+d2)/(t1+t2)5. When d1 = d2, Average Speed = 2S1S2/(S1+S2), where S1 and S2 are the speeds for covering d1 and d2 respectively. 6. When t1 = t2, Average Speed = (S1+S2)/2, where S1 and S2 are the speeds during t1 and t2 respectively. 7. Relative speed when moving in opposite direction is S1+S28. Relative speed when moving in same direction is S1-S29. A person goes certain distance (A to B) at a speed of S1 kmph and returns back (B to A) at a speed of S2 kmph. If he takes T hours in all, the distance between A and B is T(S1S2/(S1+S2)10. If two persons A and B start at the same time from two points P and Q towards each other and after crossing they take T1 and T2 hours in reaching Q and P respectively, then (A’s speed) / (B’s speed) = √T2 / √T1 Examples: 1. A man goes from A to B at a speed of 20 kmph and comes back to A at a speed of 30 kmph. Find his averagespeed for the entire journey? A. 20 kmph B. 24 kmph C. 28 kmph D. 32 kmph Answer: B. 24 kmph Explanation: Distance from A and B be 'd' Average Speed = total distance / total time Average Speed = (2d) / [(d/20) + (d/30)] = (2d) / [5d/60) => 24 kmph 2. Convert the 13/36 m/s into kilometers per hour? A. 1.2 kmph B. 1.3 kmph C. 1.4 kmph D. 1.5 kmph Answer: B. 1.3 Explanation: 13/36 m/s = 13/36 * 18/5 = 13/10 = 1.3 kmph 3. If a man can cover 12 metres in one second, how many kilometres can he cover in 3 hours 45 minutes? A. 150 kms B. 156 kms C. 162 kms D. 168 kms Answer: C. 162 kms Explanation: 12 m/s = 12 * 18/5 kmph 3 hours 45 minutes = 3 3/4 hours = 15/4 hours Distance = speed * time = 12 * 18/5 * 15/4 km = 162 kms 4. Nikita takes as much time in running 18 meters as a car takes in covering 48 meters. What will be thedistance covered by Nikita during the time the car covers 1.6 km? A. 480 m B. 520 m C. 600 m D. 800 m Answer: C. 600 m Explanation: Distance covered by Amar = 18/4.8 (1.6km) = 3/8(1600) = 600 m 5. By travelling at 40 kmph, a person reaches his destination on time. He covered two-third the total distance in one-third of the total time. What speed should he maintain for the remaining distance to reach hisdestination on time? A. 15 kmph B. 20 kmph C. 25 kmph D. 30 kmph Answer: B. 20 kmph Explanation: Let the time taken to reach the destination be 3x hours. Total distance = 40 * 3x = 120x km He covered 2/3 * 120x = 80x km in 1/3 * 3x = x hours So, the remaining 40x km, he has to cover in 2x hours would be required speed = 40x / 2x = 20 kmph 6. What distance will be covered by a bus moving at 72 kmph in 30 seconds?A. 450 m B. 500 m C. 600 m D. 750 m Answer: C. 600 m Explanation: 72 kmph = 72 * 5/18 = 20 mps D = Speed * time = 20 * 30 = 600 m 7. Walking with 4/5 of my usual speed, I miss the bus by 5 minutes. What is my usual time? A. 15 mins B. 20 mins C. 25 mins D. 30 mins Answer: B. 20 mins Explanation: Speed Ratio = 1:4 / 5 = 5:4 Time Ratio = 4:51 -------- 5 4 --------- ? => 20 8. Walking 7/6 of his usual rate, a boy reaches his school 4 minutes early. Find his usual time to reach theschool? A. 24 mins B. 26 mins C. 28 mins D. 30 mins Answer: C. 28 mins Explanation: Speed Ratio = 1:7/6 = 6:7 Time Ratio = 7:6 1 -------- 7 4 -------- ? => 28 mins