[Quantitative Aptitude/SBIPO/SSC/CLAT/GMAT/Placement Drives] - Speed,Distance and Time Part-1

One can always expect 2-3 questions from this topic in any competitive exam. The problems from this topic can be very complex in nature as it involves various logical concepts.Thus it becomes imperative to deeply understand the fundamentals of this chapter.

Note :

To solve any problem all units in the question must be uniform i.e. either all of them in m/s or km/hr.

Thus we must remember the conversion.

1 km/hr = 5 / 18 m/s                  and                               1 m/s = 18/5 km/hr


Questions based on these concepts :

Q1. Speed of Milkha Singh is 40km/hr and Speed of Forrest Gump is 30km/hr.What's the ratio of time taken by them to cover the same distance ?

Q2. Milkha takes half the time taken by Forrest to run the same distance. Forrest takes 2 hours.What is the speed of Milkha if the speed of Forrest is 20 Km/hr ?

Explanation : There is nothing much to explain in question one. In Q2, we can easily arrive at the Ratio of speeds of Milkha and Forrest is inversely proportional to the Raio of Time taken by them, which makes it 2 : 1.

Now Speed of Forrest is 20 km/hr which is 20 times 1 therefore, speed of Milkha should be 20 times 2 = 40 Km/hr (Ans).





Let's have a look at an important concept now; using LCM in TSD

Concept : If two speeds are given in the question assume distance to be LCM of both the speeds

*We used similar concept in Time and Work

Illustration :

Q. Hanuman travel half of his journey to Lanka from the Himalayas at the speed of 120km/hr and the rest half at 80 km/hr. What's his average speed ?

  Sol. इसमें क्या रखा है जोड़ो दोनों को और २ का भाग देदो  but that's not the way.

Q. The distance of the office and the home of Mussaddilal is 80 km.One day he was late by 1 hour than the normal time to leave for the office so he increased his speed by 4 km/hr and thus he reached the office at normal time.What's the original and changed speed of Mussaddilal  ?

Method of Product Consistency

• We know that Distance  = Speed * Time
• Given that Distance is constant; If Speed or Time is increased by 1/P then Time or Speed is decreased by 1/P+1
• Given that Distance is constant; If Speed or Time is decreased by 1/P then Time or Speed is increased by 1/P-1

Application : 

Q. Rohit  goes to School at the speed of 20 km/hr and reaches school 4 min late.Next time(After meeting Jadoo/After Drinking Bournvita) , he goes at 25 km/hr and reaches school 2 minutes earlier than the scheduled time.What is the distance to the school ?

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Practice as many questions as possible w/o paper and pen based on these concepts.

In the subsequent parts we will see Relative motion, Circular motion and Boats and Streams

Happy Learning :)