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) 15$1/2$ km/hr
(b) 16 km/hr
(c) 14$2/5$ km/hr
(d) 15 km/hr
The correct answers to the above question in:
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
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Read more problems on average speed Based Quantitative Aptitude Questions and Answers
Question : 1
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 : 2
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 : 3
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 : 4
A car completed a journey of 400 km in 12$1/2$ hrs. The first $3/4$th of the journey was done at 30 km/hr. Calculate the speed for the rest of the journey.
a) 40 km/hr
b) 30 km/hr
c) 45 km/hr
d) 25 km/hr
Answer »Answer: (a)
Total distance covered = 400 km.
Total time = $25/2$ hours
$3/4$th of total journey
= $3/4$ × 400 = 300 km.
Time taken = $\text"Distance"/ \text"Speed"$
= $300/30$ = 10 hours
Remaining time = $25/2$ –10
= ${25 - 20}/2 = 5/2$ hours
Remaining distance = 100 km.
∴ Required speed of car
= $100/{5/2} = {100 × 2}/5$ = 40 kmph.
Question : 5
A man goes from A to B at a uniform speed of 12 kmph and returns with a uniform speed of 4 kmph His average speed (in kmph) for the whole journey is :
a) 6
b) 4.5
c) 8
d) 7.5
Answer »Answer: (a)
Using Rule 5,
If two equal distances are covered at two unequal speed of x kmph and y kmph,
then average speed = $({2xy}/{x + y})$
= ${2 × 12 × 4}/{12 + 4} = 96/16$ = 6 kmph
Question : 6
A train travelled at a speed of 35 km/hr for the first 10 minutes and at a speed of 20 km/hr for the next 5 minutes. The average speed of the train for the total 15 minutes is
a) 31 km/hr
b) 29 km/hr
c) 30 km/hr
d) 23 km/hr
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= $\text"total travelled distance"/\text"total time taken in travelling distance"$= ${d_1 + d_2 + d_3 +...}/{t_1 + t_2 + t_3 +...}$
Distance covered
= $(35 × 10/60 + 20 × 5/60)$ km
= $(35/6 + 10/6) = 45/6$ km
Total time = 15 minutes
= $1/4$ hour
Required average speed
= $\text"Distance covered"/ \text"Time taken"$
= $45/6 × 4$ = 30 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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