# Aptitude - Races and Games - Discussion

### Discussion :: Races and Games - General Questions (Q.No.2)

2.

A and B take part in 100 m race. A runs at 5 kmph. A gives B a start of 8 m and still beats him by 8 seconds. The speed of B is:

 [A]. 5.15 kmph [B]. 4.14 kmph [C]. 4.25 kmph [D]. 4.4 kmph

Explanation:

 A's speed = 5 x 5 m/sec = 25 m/sec. 18 18

 Time taken by A to cover 100 m = 100 x 18 sec = 72 sec. 25

Time taken by B to cover 92 m = (72 + 8) = 80 sec.

 B's speed = 92 x 18 kmph = 4.14 kmph. 80 5

 Naresh.Ravula said: (Dec 21, 2010) While finding the speed of the B, why we are using the 92m only instead of 100m?

 Sanju said: (May 15, 2011) Out of 100m he ran 8m so we deduct 8m from 100m then we get 92m to obtain B Speed we should caluclate B Speed by using 92m instead of 100m. I hope you understand. !

 Rajesh said: (Sep 18, 2011) We should understand the ques properly. Its in the ques that b is 8m forward than a in 100m race, am I right?

 Padma said: (Sep 24, 2011) Here first we can find the losers time, secondly we can find losers distance[since losers distance=winners distance- (start distance+beat distance) ] and later we can find the speed of B[since speed=distance/time]. Which is the final answer. Is this not the correct procedure. Please tell me if it is.

 Baburaj said: (Dec 16, 2011) Why Time taken by B to cover 92 m = (72 + 8) = 80 sec. comes? Can any one explain ?

 Sudharshan Madgula said: (Jan 16, 2012) @Baburaj: Because A is taking 72sec to run 100m and beats B by 8sec. that means still B needs 8sec to complete 100m. therefore time taken by B to complete 92m is 72+8=80sec.

 Anamika Sinha said: (Jan 21, 2012) How did you get A's speed ? I dint understand. Please explain.

 Sayed said: (Jan 21, 2012) How A's speed is found ?

 Jaanvi said: (Jan 23, 2012) @anamika & sayed A's speed is in kmph. to make it in m/s, 5 is multiplied with 1000/(60X60). Hence, 5X5/18=25/18

 Sag said: (Aug 25, 2012) We are adding 8 second to cmplete 100m for b. So why his speed is calulated for 92 m. It should be for 100m and answer should be 4. 25.

 Mangesh said: (Sep 18, 2012) Since both are covering 100m finally. So why we took 92m instead 100m ?

 Qwaci said: (Nov 22, 2012) @ Sag & Mangesh. First of all, A gave B a start of 8m so B did not run 100m but 92m (100m-8m). Secondly, A took 72sec to cover the 100m and still won B who had only 92m to run by 8sec which means that with the 92m that B covered he used or needed 80sec (72sec+8sec). I hope my little explanation could help you understand.

 Prafull Gadekar said: (Jun 24, 2013) Instead of taking 5/18, we solve like, A 's speed = 5 kmph = 5000 mph = 5000/3600 = 1.38m/sec, For 100m distance time = 72.3 sec or 72 sec, B's require time to cover 92m distance=(72+8) = 80 sec. 80 sec- 92m then, 1 sec - 1.15m. 1.15m/sec. 1.15*3600 = 4140 mph = 4.14 kmph.

 Girijesh said: (Aug 4, 2013) Let speed of B is x meter/sec. Speed of A is y meter/sec. Total time to reach 100 meter by A is 100m/5kmph = 72 sec. Total time to reach 100 meter by B is: (8/x) + time taken by A + 8 = 100/x. (8/x) + 72 + 8 = 100/x. x = 92/80 m/s = 4.14 kmph.

 Prasanna said: (Aug 30, 2013) Why can't we change the distance into km and solve?. I am not getting the answer in that way.

 Buddhika said: (Dec 30, 2014) Forget 5 kmh. A runs = 8 m. B runs = 100-8 = 92 m. B speed = 92 m/8 s = 11.5 ms. Now we convert ms = kmh. 11.5 x 18/5 = 4.14 kmh. That is all.

 Deepali said: (May 26, 2015) How get 18?

 Vinay said: (Sep 25, 2015) We have given speed of A = 5 km/h => 5x5/18 = (25/18) speed; A takes time = 100x (18/25), Time = Distance/Speed; =72 sec; Since A beat B by 8 sec. So total time taken by B = 72+8 = 80 (time); Since A gives 8 m to B. So total distance cover by B = 100-8 = 92 (dist); We know that Speed = Distance/Time; Now speed of B = 92/80 m/s; Now converting it into km/h => (92/80) x (18/5). => 4.4 answer.

 Manisha said: (May 26, 2016) I can't understand why we have to use 18/5, where it come from? Can anyone explain?

 Sravs said: (Jun 22, 2016) 18/5 is the conversion of m/s to km/hr. Because option is in km/hr. We need to convert.

 Ashutosh Kumar said: (Sep 2, 2016) A --> 100m. B --> 92m. Above is the situation B covers 92m in 72 + 8 = 80s therefore we have taken 92m to calculate the speed of B.

 Mariyappa said: (Mar 24, 2017) How get 18 came here?

 Sairam said: (Mar 4, 2019) Actually, B has to complete 92 meters in 72 seconds but he is taking an extra 8 seconds time to complete 100 meters which can be concluded from the question. Am I right?

 Sileshi said: (May 23, 2019) How come 5/18? Please tell me.

 Rocktim said: (Jul 5, 2019) How come 5/18? Please tell me.

 Manikanta said: (Aug 12, 2019) Here A runs for 100meters while B has to run only for 92Meters as B is 8meters ahead of A. 5km per hour=5000 meters per hour. As the question is asking in seconds. Now convert for each second how many meters A is running. Here we have 3600 seconds for one hour. So 5000meters or 5*1000meters/3600 which comes to 5*5/18=25/18. In how many seconds A ran the100meters =100m*25/18sec=72sec. A has run 8seconds faster than B. Which means B took 8seconds more to complete the run. Therefore 72+8=80Sec. Now the question is B's speed in km per hour. Calculate for each sec how many meters he ran=92meters/80sec. Hence=92/80*18/5 (lets say 3600sec/1000meters) =4.14kmph.

 Anusha said: (Jun 18, 2020) Nice explanation, thanks @Buddhika.