Model 3 Problems on average speed Section-Wise Topic Notes With Detailed Explanation And Example Questions
MOST IMPORTANT quantitative aptitude - 5 EXERCISES
The following question based on time & distance topic of quantitative aptitude
(a) 35
(b) 45
(c) 42
(d) 40
The correct answers to the above question in:
Answer: (d)
Using Rule 2,
Total distance = 100 km.
Total time = $50/50 + 40/40 + 10/20$
= $1 + 1 + 1/2 = 5/2$ hours
Average speed = ${100 × 2}/5$ = 40 kmph
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Read more problems on average speed Based Quantitative Aptitude Questions and Answers
Question : 1
P travels for 6 hours at the rate of 5 km/ hour and for 3 hours at the rate of 6 km/ hour. The average speed of the journey in km/ hour is
a) 1$2/9$
b) 2$2/5$
c) 3$1/5$
d) 5$1/3$
Answer »Answer: (d)
Using Rule 2,If a man travels different distances $d_1,d_2,d_3$,... and so on in different time $t_1,t_2,t_3$ respectively then,Average speed= $\text"total travelled distance"/\text"total time taken in travelling distance"$= ${d_1 + d_2 + d_3 +...}/{t_1 + t_2 + t_3 +...}$
Total distance
= 5 × 6 + 3 × 6
= 30 + 18 = 48 km
Total time = 9 hours
Average speed
= $48/9 = 16/3 = 5{1}/3$ kmph
Question : 2
The speed of a train going from Nagpur to Allahabad is 100 kmph while its speed is 150 kmph when coming back from Allahabad to Nagpur. Then the average speed during the whole journey is :
a) 140 kmph
b) 135 kmph
c) 120 kmph
d) 125 kmph
Answer »Answer: (c)
Using Rule 5,
Here, the distances are equal.
Average speed
= $({2 × 100 × 150}/{100 + 150})$ kmph
= ${2 × 100 × 150}/250$ = 120 kmph
Question : 3
A train covers a distance of 3584 km in 2 days 8 hours. If it covers 1440 km on the first day and 1608 km on the second day, by how much does the average speed of the train for the remaining part of the journey differ from that for the entire journey ?
a) 4 km/hour more
b) 5 km/hour less
c) 3 km/hour more
d) 3 km/hour less
Answer »Answer: (c)
Using Rule 2,If a man travels different distances $d_1,d_2,d_3$,... and so on in different time $t_1,t_2,t_3$ respectively then,Average speed= $\text"total travelled distance"/\text"total time taken in travelling distance"$= ${d_1 + d_2 + d_3 +...}/{t_1 + t_2 + t_3 +...}$
Remaining distance
= (3584 - 1440 - 1608) km
= 536 km.
This distance is covered at the rate of $536/8$ = 67 kmph.
Average speed of whole journey
= $3584/56$ = 64 kmph
Required difference in speed
= (67 - 64) kmph i.e. = 3 kmph more
Question : 4
A bus covers four successive 3 km stretches at speed of 10 km/ hr, 20 km/hr, 30 km/hr and 60 km/hr respectively. Its average speed over this distance is
a) 20 km/hr
b) 10 km/hr
c) 30 km/hr
d) 25 km/hr
Answer »Answer: (a)
Using Rule 3,If a man travels different distances $d_1,d_2,d_3$, and so on with different speeds $s_1,s_2,s_3$, respectively then,Average speed = $({d_1 + d_2 + d_3 + ...})/{d_1/S_1 + d_2/S_2 + d_3/S_3 + ...}$
Average speed
= $\text"Total distance"/ \text"Time taken"$
= $12/{3/10 + 3/20 + 3/30 + 3/60}$
= $12/{3({6 + 3 + 2 + 1}/60)}$
= ${12 × 60}/{3 × 12} = 20$ kmph
Question : 5
A bus travels 150 km in 3 hours and then travels next 2 hours at 60 km/hr. Then the average speed of the bus will be
a) 50 km/hr.
b) 60 km/hr.
c) 55 km/hr.
d) 54 km/hr.
Answer »Answer: (d)
Total distance covered by the bus
= 150 km. + 2 × 60 km.
= (150 + 120) km.
= 270 km.
∴ Average speed = $\text"Total distance"/ \text"Time taken"$
= $270/5$ = 54 kmph.
Question : 6
A and B are 20 km apart. A can walk at an average speed of 4 km/ hour and B at 6 km/hr. If they start walking towards each other at 7 a.m., when they will meet ?
a) 9.00 a.m.
b) 10.00 a.m.
c) 8.00 a.m.
d) 8.30 a.m.
Answer »Answer: (a)
Using Rule 11,Time taken by 1st man to reach B after meeting 2nd man at C is '$t_1$' and time taken by 2nd man to reach A after meeting 1st man at C is '$t_2$' then:${\text"Speed of 1st man"(s_1)}/{\text"Speed of 2nd man"(s_2)} = √{t_2/t_1}$Distance from A to B = $s_1t_1 + S_2t_2$
If A and B meet after t hours, then
4 t + 6 t = 20
10 t = 20 ⇒ t = $20/10$ = 2 hours.
Hence, both will meet at 9 a.m.
GET time & distance PRACTICE TEST EXERCISES
Model 1 Basic Time & Distance using formula
Model 2 Vehicles in x/y of its usual speed
Model 3 Problems on average speed
Model 4 Time & Distance with Ratios
Model 5 Problems with Races
time & distance Shortcuts and Techniques with Examples
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Model 1 Basic Time & Distance using formula
Defination & Shortcuts … -
Model 2 Vehicles in x/y of its usual speed
Defination & Shortcuts … -
Model 3 Problems on average speed
Defination & Shortcuts … -
Model 4 Time & Distance with Ratios
Defination & Shortcuts … -
Model 5 Problems with Races
Defination & Shortcuts …
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