# Boats and Streams Quiz Set 015

### Question 1

A boat travels a downstream distance of 28 km in 2 hours, and an upstream distance of 56 km in 7 hours. What is the speed of the stream?

A

3 kmph.

B

4 kmph.

C

2 kmph.

D

6 kmph.

Soln.
Ans: a

The downstream speed = \$28/2\$ = 14 km/h, and the upstream speed = \$56/7\$ = 8 km/h. By the shortcut method, the speed of the stream is half of the difference between the downstream and upstream speeds of the boat. So the required speed = \${14 - 8}/2\$ = 3 km/h.

### Question 2

A boat travels a downstream distance of 60 km in 5 hours, and an upstream distance of 30 km in 5 hours. What is the speed of the stream?

A

3 kmph.

B

4 kmph.

C

2 kmph.

D

6 kmph.

Soln.
Ans: a

The downstream speed = \$60/5\$ = 12 km/h, and the upstream speed = \$30/5\$ = 6 km/h. By the shortcut method, the speed of the stream is half of the difference between the downstream and upstream speeds of the boat. So the required speed = \${12 - 6}/2\$ = 3 km/h.

### Question 3

If the speed of a boat in the direction of the stream current is 24 km/h, and the speed of the current is 10 km/h, what would be the speed of the boat against the current?

A

4 km/h.

B

5 km/h.

C

3 km/h.

D

7 km/h.

Soln.
Ans: a

Speed of the boat in still water is the difference between its downstream speed and the speed of the stream, which is 24 - 10 = 14 km/h. Hence, the speed of the boat against the current is 14 - 10 = 4 km/h.

### Question 4

A boat can travel 252 km downstream in 18 hours. If it covers the same distance upstream in 42 hours, what is the rate of flow of the stream?

A

4 kmph.

B

5 kmph.

C

3 kmph.

D

7 kmph.

Soln.
Ans: a

The downstream speed = \$252/18\$ = 14 km/h, and the upstream speed = \$252/42\$ = 6 km/h. By the shortcut method, the speed of the stream is half of the difference between the downstream and upstream speeds of the boat. So the required speed = \${14 - 6}/2\$ = 4 km/h.

### Question 5

A boat has a downstream speed of 16 km/h and an upstream speed of 6 km/h. What is the speed of the stream?

A

5 kmph.

B

6 kmph.

C

4 kmph.

D

8 kmph.

Soln.
Ans: a

By the shortcut method, the speed of the stream is half of the difference between the downstream and upstream speeds of the boat. So the required speed = \${16 - 6}/2\$ = 5 km/h. 