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) 50 km/hr.
(b) 60 km/hr.
(c) 55 km/hr.
(d) 54 km/hr.
The correct answers to the above question in:
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.
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Read more problems on average speed Based Quantitative Aptitude Questions and Answers
Question : 1
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 : 2
On a journey across Kolkata, a taxi averages 50 km per hour for 50% of the distance, 40 km per hour for 40% of it and 20 km per hour for the remaining. The average speed (in km/hour) for the whole journey is :
a) 35
b) 45
c) 42
d) 40
Answer »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
Question : 3
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 : 4
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.
Question : 5
A train moves with a speed of 30 kmph for 12 minutes and for next 8 minutes at a speed of 45 kmph. Find the average speed of the train:
a) 48 kmph
b) 30 kmph
c) 37.5 kmph
d) 36 kmph
Answer »Answer: (d)
Using Rule 3,
Average speed
= $\text"Total distance"/\text"time taken"$
= ${30 × 12/60 + 45 × 8/60}/{12/60 + 8/60}$
= 12 × 3 = 36 kmph
Question : 6
A man goes from a place A to B at a speed of 12 km/hr and returns from B to A at a speed of 18 km/hr. The average speed for the whole journey is
a) 15$1/2$ km/hr
b) 16 km/hr
c) 14$2/5$ km/hr
d) 15 km/hr
Answer »Answer: (c)
Using Rule 5,
Average speed
= $({2xy}/{x + y})$ kmph
= $({2 × 12 × 18}/{12 + 18})$ kmph
= $({2 × 12 × 18}/30)$ kmph
= 14$2/5$ kmph
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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