PE 2 - Time, Speed & Distance | Arithmetic - Time, Speed & Distance
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A man can row 4.5 km/h in still water and he finds that it takes him twice as long to row up as to row down the river. Find the rate of the stream.
- (a)
1.5 kmph
- (b)
2 kmph
- (c)
2.5 kmph
- (d)
1.75 kmph
Answer: Option A
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Explanation :
If the rate of the stream is x, then 2(4.5 – x) = 4.5 + x
⇒ 9 – 2x = 4.5 + x
⇒ 3x = 4.5
⇒ x = 1.5 km/hr
Hence, option (a).
Workspace:
A car travels the first one-third of a certain distance with a speed of 10 km/h, the next one-third distance with a speed of 20 km/h, and the last one-third distance with a speed of 60 km/h. The average speed of the car for the whole journey is
- (a)
18 kmph
- (b)
24 kmph
- (c)
30 kmph
- (d)
36 kmph
Answer: Option A
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Explanation :
Let the whole distance travelled be x km and the average speed of the car for the whole journey be y km/hr.
Then,
⇒
⇒ = 1
⇒ y = 18 km/hr
Hence, option (a).
Workspace:
Two runners run in the same direction along a circular track of 2 km long. The faster runner overtakes the slower one in every 30 minutes. Find their speeds if the faster one completes the track one minute sooner than the other.
- (a)
24 km/h and 20 km/h
- (b)
44 km/h and 28 km/h
- (c)
20 km/h and 18 km/h
- (d)
20 km/h and 16 km/h
Answer: Option A
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Explanation :
Let x km/h and y km/h be the speeds of the two runners x > y
As per the question, …(1)
Also faster runner covers (x – y) km more than slower in 1 hr.
So, he will gain 2 km in hr or 1/2 hr. (30 min)
or, x – y = 4 …(2)
On solving (1) and (2), we get x = 24 km/h y = 20 km/h
Hence, option (a).
Workspace:
Two trains are moving in opposite directions at speeds of 60 km/h and 90 km/h. Their lengths are 1.10 km and 0.9 km respectively. The time taken by the slower train to cross the faster train in seconds is
- (a)
36
- (b)
49
- (c)
45
- (d)
48
Answer: Option D
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Explanation :
Relative speed of both trains = 60 + 90 = 150 km/hr
Total distance = 1.10 + 0.9 = 2 km
∴ Required time = (2 × 60 × 60)/150 = 48 seconds
Hence, option (d).
Workspace:
A is twice as fast as B and B is thrice as fast as C is the journey covered by C in 1½ hours will be covered by A in
- (a)
15 minutes
- (b)
2 minutes
- (c)
30 minutes
- (d)
1 hour
Answer: Option A
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Explanation :
According to question,
A : B : C
2 : 1 :
3 : 1
A : B : C
6 : 3 : 1 →Ratio of speed
1/6 : 1/3 : 1/1 →Ratio of Time
Since, time ∝ 1/speed
⇒ 1 : 2 : 6
↓ 1/4
3/2
∴ Time taken by A = 1 × 1/4 = 15 minutes
Hence, option (a).
Workspace:
A motorcyclist covered two thirds of a total journey at his usual speed. He covered the remaining distance at three fourth of his usual speed. As a result, he arrived 30 minutes later than the time he would have taken at usual speed. If the total journey was 180 km, then what is his usual speed?
- (a)
40 kmph
- (b)
36 kmph
- (c)
30 kmph
- (d)
32 kmph
Answer: Option A
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Explanation :
Total journey = 180 km
1/3rd of journey = 180/3 = 60 km.
If usual speed be x km/h, then
⇒
⇒
⇒ x = 40 km/h
Hence, option (a).
Workspace:
A man can row a certain distance against the stream in six hours. However, he would take two hours less to cover the same distance with the current. If the speed of the current is 2 km/h, then what is the rowing speed in still water?
- (a)
10 kmph
- (b)
12 kmph
- (c)
14 kmph
- (d)
8 kmph
Answer: Option A
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Explanation :
If the rowing speed in still water be x km/h, and the distance by y km, then
6
⇒ y = 6(x - 2) …(1)
and, = 4
⇒ y = 4(x + 2) …(2)
⇒ 6(x - 2) = 4(x + 2)
⇒ x = 10 km/h
Hence, option (a).
Workspace:
Two trains X and Y leave stations A and B, respectively, which are 180 km apart. Train X travels at a speed of 70 km/hr non-stop towards B. Train Y travels at 50 km/hr towards A, but stops for 15 min at a station known to be 50 km away from station B. At what approximate distance (in km) from station A will both the trains meet?
- (a)
112
- (b)
118
- (c)
120
- (d)
150
- (e)
122
Answer: Option A
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Explanation :
Total time taken by Y to cover 50 km = 50/50 = 1 hr.
It stops at station C for ¼ hr.
Now, in (1 + 1/4) hr, train X travels 70 × 5/4 = 87.5 km
This means they do not cross each other by the time train Y finishes its stop at station C.
Let them meet after t hr.
Then, 70t + 50 = 180
⇒ t = 192.5/120 hr
Distance from A = km = 112 km (approximately).
Hence, option (a).
Workspace:
If I walk at 4 km/h, I miss the bus by 10 minutes. If I walk at 5 km/h, I reach 5 minutes before the arrival of the bus. How far I walk to reach the bus stand?
- (a)
5 kms
- (b)
4.5 kms
- (c)
5.25 kms
- (d)
Cannot be determined
Answer: Option A
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Explanation :
d = product of speed
d = [Here, -ve sign indicates before the schedule time]
⇒ d = 5 km
Hence, option (a).
Workspace:
Three men A, B and C walk around a circular path of length 1760 meters at the rate of 160, 120, 105 m/minutes respectively. If they start together and walk in the same direction, when will they first be together again?
- (a)
5 hours 50 mins
- (b)
5 hours 52 mins
- (c)
6 hours 45 mins
- (d)
None of these
Answer: Option B
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Explanation :
A gains (160 – 120) 40 m/min. over B and A gains (160 – 105) 88 m/min. over C so A will gain 1760 m
→ over B in 1760/40 = 44 mins
→ over C in 1760/55 = 32 mins
The three will be together when time will be LCM or multiple of LCM of 32 and 44 i.e., 352 min. or after 5 hours 52 min.
Hence, option (b).
Workspace:
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