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) 55 km/hr
(c) 30 km/hr
(d) 45 km/hr
The correct answers to the above question in:
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 covered by train in 5 minutes
= (500 + 625 + 750 + 875 + 1000) metre
= 3750 metre = 3.75 km.
Time = 5 minutes
= $5/60$ hour = $1/12$ hour
Speed of train = Distance Time
= $(3.75/{1/12})$ kmph
= (3.75 × 12) kmph = 45 kmph
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Read more problems on average speed Based Quantitative Aptitude Questions and Answers
Question : 1
Gautam goes to office at a speed of 12 kmph and returns home at 10 kmph. His average speed is :
a) 10.9 kmph
b) 12.5 kmph
c) 11 kmph
d) 22 kmph
Answer »Answer: (a)
Here distances are same.
∴ Average speed = $({2xy}/{x + y})$ kmph
= $({2 × 12 × 10}/{12 + 10})$ kmph
= $(240/22)$ kmph = 10.9 kmph
Question : 2
With an average speed of 40 km/ hr, a train reaches its destination in time. If it goes with an average speed of 35 km/hr, it is late by 15 minutes. The total journey is
a) 70 km
b) 80 km
c) 30 km
d) 40 km
Answer »Answer: (a)
Let the length of journey be x km, then
$x/35 - x/40 = 15/60 = 1/4$
${8x - 7x}/280 = 1/4$
$x = 280/4 = 70$ km
Question : 3
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
Question : 4
When Alisha goes by car at 50 kmph, she reaches her office 5 minutes late. But when she takes her motorbike, she reaches 3 minutes early. If her office is 25 kms away, what is the approximate average speed at which she rides her motorbike ?
a) 58 kmph
b) 52 kmph
c) 68 kmph
d) 62 kmph
Answer »Answer: (c)
Difference of time
= 5 + 3 = 8 minutes
= $8/60$ hour = $2/15$ hour
If the speed of motorbike be x kmph, then
$25/50 - 25/x = 2/15$
$25/x = 1/2 - 2/15$
$25/x = {15 - 4}/30 = 11/30$
11x = 25 × 30
$x = {25 × 30}/11 = 750/11$
= 68.18 kmph ≈ 68 kmph
Question : 5
A car travels from A to B at the rate of 40 km/h and returns from B to A at the rate of 60 km/ h. Its average speed during the whole journey is
a) 45 km/h
b) 60 km/h
c) 48 km/h
d) 50 km/h
Answer »Answer: (c)
Here, distance is same.
Average speed = ${2xy}/{x + y}$
= $({2 × 40 × 60}/{40 + 60})$ kmph.
= $({2 × 40 × 60}/100)$ kmph.
= 48 kmph.
Question : 6
A man covers the journey from a station A to station B at a uniform speed of 36 km/hr and returns to A with a uniform speed of 45 km/hr. His average speed for the whole journey is :
a) 41 km/hr
b) 42 km/hr
c) 40 km/hr
d) 40.5 km/hr
Answer »Answer: (c)
Using Rule 5,
Here same distances are covered at different speeds.
Average speed
= $({2xy}/{x + y})$ kmph
= $[{2 × 36 × 45}/({36 + 45})]$ kmph
= ${2 × 36 × 45}/81$ = 40 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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