Practice Questions for Time, Speed & Distance

1. CRE 4 - Boats & Streams | Time, Speed & Distance

The speed of a boat in still water is 60 kmph and the speed of the current is 20 kmph. Find the speed downstream and upstream

(a)
35, 25 kmph
(b)
40, 60 kmph
(c)
50, 55 kmph
(d)
80, 40 kmph

2. CRE 4 - Boats & Streams | Time, Speed & Distance

The speed of a boat in still water is 2 km/h If its speed upstream is 1 km/h, then speed of the stream is :

(a)
2 kmph
(b)
3 kmph
(c)
1 kmph
(d)
None of these

3. CRE 4 - Boats & Streams | Time, Speed & Distance

A man can row with the stream at 10 km/h and against the stream at 5 km/h. Man’s speed in still water is :

(a)
5 kmph
(b)
2.5 kmph
(c)
7.5 kmph
(d)
15 kmph
(e)
None of these

4. CRE 4 - Boats & Streams | Time, Speed & Distance

A boat goes 40 km upstream in 8 hours and a distance of 36 km downstream in 6 hours. The speed of the boat in standing water is :

(a)
6.5 kmph
(b)
6 kmph
(c)
5.5 kmph
(d)
5 kmph

5. CRE 4 - Boats & Streams | Time, Speed & Distance

A man can row 6 kmph in still water. When the river is running at 1.2 kmph, it takes him 10 hours to row to a place and back. How far is the place?

(a)
31.2 kmph
(b)
28.8 kmph
(c)
30 kmph
(d)
20 kmph

6. CRE 4 - Boats & Streams | Time, Speed & Distance

A boatman can row 1 km against the stream in 20 minutes and return in 18 minutes. Find the rate of current

(a)
1/3 kmph
(b)
1/6 kmph
(c)
5/6 kmph
(d)
None of these

Answer: Option B

Explanation :

Speed of the boatman upstream = $\frac{1}{\frac{20}{60}}$ = 3 km/hr.

Speed of the boatman downstream = $\frac{1}{\frac{18}{60}}$ = 10/3 km/hr.

Rate of current = $\frac{d o w n s t r e a m s p e e d - u p s t r e a m s p e e d}{2}$ = (10/3 - 3)/2 = 1/6 km/hr.

Hence, option (b).

7. CRE 4 - Boats & Streams | Time, Speed & Distance

A boat travels at a speed of 15 kmph. It travels between points A and B, which are 200 km apart. If the boat goes downstream from A to B in 10 hours, how long will it take to return upstream from B to A (in hours)?

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Answer: 20

Explanation :

S_down= 15 + S_s

T = $\frac{D}{S_{d o w n}} = \frac{200}{15 + S_{s}}$

10 = $\frac{200}{15 + S_{s}}$

15 + S_s = 200/10 = 20

S_s = 5 kmph

T = $\frac{D}{S_{u p}} = \frac{200}{15 - 5}$

Hence, 20.

8. CRE 4 - Boats & Streams | Time, Speed & Distance

Two boats, travelling at 5 and 10 kms per hour, head directly towards each other. They begin at a distance of 20 kms from each other. How far apart are they (in kms) two minutes before they collide?

(a)
1/12
(b)
1/6
(c)
1/4
(d)
1/2

9. CRE 4 - Boats & Streams | Time, Speed & Distance

A boat can travel 10 km upstream in 2 hours. If the speed of the boat becomes half, then the return journey also takes the same time. What is the speed of water flow?

(a)
5/3 kmph
(b)
10/3 kmph
(c)
7/3 kmph
(d)
8/3 kmph
(e)
5/2 kmph

Answer: Option A

Explanation :

Let the speed of the boat be Vb and that of the stream be V_w.

Now, the time taken by the boat in going upstream = $\frac{10}{V_{b} - V_{w}}$ = 2

⇒ V_b - V_w = 5 ... (i)

And the time taken by the boat in going downstream = $\frac{10}{\frac{V_{b}}{2} + V_{w}}$ = 2

⇒ V_b/2 + V_w = 5 ... (ii)

Adding (i) and (ii),

(3V_b)/2 = 10

V_b= 20/3

V_w = 5 - (10/3) = 5/3 kmph

The speed of the water flow is 5/3 kmph.

Hence, option (a).

10. CRE 4 - Boats & Streams | Time, Speed & Distance

A boat P travels 80 km upstream from point A to point B in 10 hours and downstream from point B to point A in 5 hours. Another boat Q can travel from point A to a point C 60 km upstream in 5 hours.

What is the speed of the boat Q in still water?

(a)
12 kmph
(b)
16 kmph
(c)
20 kmph
(d)
24 kmph
(e)
30 kmph

11. CRE 4 - Boats & Streams | Time, Speed & Distance

A boat starts from A and moves towards B. Another boat from B, with the same speed as that of first boat, starts moving towards A. They meet at a point which is 20 km towards B from exactly half-way of A to B and the distance between A and B is 120 km.

What is the ratio of speed of boat to that of water?

(a)
2 : 1
(b)
3 : 2
(c)
3 : 1
(d)
4 : 1
(e)
5 : 2

Answer: Option C

Explanation :

It is clear that the water flow is from A to B.

Distance travelled by boat starting from A = 80 kms.

Distance travelled by boat starting from B = 40 kms.

Since time travelled is same for both the boats:

$\frac{80}{V_{b} + V_{w}} = \frac{40}{V_{b} - V_{w}}$

⇒ V_b = 3V_w

⇒ V_b : V_w = 3 : 1

Hence, option (c).

CRE 4 - Boats & Streams | Time, Speed & Distance

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