topic badge

9.11 Flow networks

Worksheet
Flow networks
1

Consider the following networks:

Network A

Network B

Network C

a

Determine which network is a flow network.

b

State the source vertex of the flow network.

c

State the sink vertex of the flow network.

2

Consider the given flow network:

a

Which vertex is the source for this flow network?

b

Which vertex is the sink for this flow network?

Maximum flow and cuts
3

For each of the following flow networks, calculate the inflow, outflow and maximum flow for the indicated vertices:

a

For vertices 2,3, \text{and } 4

b

For vertices 2,3, 4,\text{and } 5

4

For each of the following networks, list all the cuts that are valid:

a
b
c
5

For each of the following networks, calculate the capacity through each cut:

a
b
6

Determine the capacity through each of the valid cuts of the following flow networks:

a
b
Max-flow/min-cut theorem
7

For each of the following networks, determine which of the cuts has the smallest capacity:

a
b
8

Calculate the maximum flow through the following networks:

a
b
c
Applications
9

An oil company just received their pipe maps from the engineer connecting the oil storage tank (vertex 1) to its sink (vertex 7).

Calculate the maximum flow of oil (in litres/hour) through the pipes.

10

The ventilation system of an apartment is being drafted by the engineer. The following graph represents the ducts and the maximum flow (in litres/second) in each one.

Calculate the maximum flow between the source (vertex A) and the sink node (vertex G).

11

An engineer was given the task to study the rainwater drainage in a certain area. The following graph represents the drains and their maximum capacity.

Calculate the maximum flow of rainwater (in litres/hour) in the drainage system between vertex 1 and vertex 6.

12

The following graph represents the road map between Balgownie and Kanahooka, and the maximum number of motorists that can travel on each road at one time.

a

Calculate the maximum number of vehicles that can travel from Balgownie to Kanahooka at a time.

b

How could the flow of traffic from Balgownie to Kanahooka be improved to cater for the following issues:

i

Unanderra is currently over supplied.

ii

Wollongong is currently under supplied.

iii

Port Kembla is currently over supplied.

iv

Fairy Meadow is currently under supplied.

13

A circuit involving a capacitor, three resistors and two inputs is represented by the following network, with the currents given in \text{mA}:

a

Calculate the maximum current that can flow between Power in and Power out.

b

Comment on anything you notice about the capacity through various cuts in this network.

14

The traffic flow (in hundreds of cars per hour) through a city centre is shown in the following directed network:

a

Identify the source vertex.

b

Identify the sink vertex.

c

Calculate the maximum flow through this network.

15

A network of water pipes is shown in the first figure, with the maximum flow capacity of each pipe given in litres per minute. The second figure shows a possible flow of water within the network:

a

Determine the missing values in the second figure.

b

For the flow shown in second diagram, which pipes are operating at full capacity?

c

Calculate the total flow for the second diagram.

d

It is possible to increase the flow from part (c) by 5 \text{ litres/min}. State the path that can support this extra flow.

e

Determine the flow through each of the cuts P, Q, R and S in the diagram on the right.

f

State the cut that shows the flow achieved in part (d) is a maximum for this network.

Sign up to access Worksheet
Get full access to our content with a Mathspace account

Outcomes

MS2-12-8

solves problems using networks to model decision-making in practical problems

What is Mathspace

About Mathspace