Matrix of Relation
Mathematics · FE Reference Handbook section
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
a relation matrix linking survey stations to control points Given rows (elements of the first set) (n_r) = 9.0000; columns (elements of the second set) (n_c) = 17.0000, determine the matrix entries (E) in entries.
Given
Find
matrix entries (E), in entries
Start with the thinking
- The governing relation printed in this handbook section is Entries in a relation (adjacency) matrix.
- Everything except E is given, so isolate E symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A relation between two finite sets is stored as a Boolean matrix of relation, so the storage cost is the entry count.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for E:
Step 3 — List the givens: rows (elements of the first set) (n_r) = 9.0000, columns (elements of the second set) (n_c) = 17.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning E = 153.0 entries to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 306.0 — kept a factor of two that cancels in the correct rearrangement.
- 76.5000 — dropped that same factor in the other direction.
- 168.3 — rounded an intermediate value before the final step.
Reference: FE Handbook — Discrete Mathematics (Matrix of Relation)
a finite state machine transition table stored as a Boolean matrix Given matrix entries (E) = 232.0 entries; columns (elements of the second set) (n_c) = 9.0000, determine the rows (elements of the first set) (n_r).
Given
Find
rows (elements of the first set) (n_r)
Start with the thinking
- The governing relation printed in this handbook section is Entries in a relation (adjacency) matrix.
- Everything except n_r is given, so isolate n_r symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A relation between two finite sets is stored as a Boolean matrix of relation, so the storage cost is the entry count.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for n_r:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning n_r = 25.7778 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 51.5556 — kept a factor of two that cancels in the correct rearrangement.
- 12.8889 — dropped that same factor in the other direction.
- 28.3556 — rounded an intermediate value before the final step.
Reference: FE Handbook — Discrete Mathematics (Matrix of Relation)
a relation matrix linking pipe nodes to demand nodes Given matrix entries (E) = 353.0 entries; rows (elements of the first set) (n_r) = 18.0000, determine the columns (elements of the second set) (n_c).
Given
Find
columns (elements of the second set) (n_c)
Start with the thinking
- The governing relation printed in this handbook section is Entries in a relation (adjacency) matrix.
- Everything except n_c is given, so isolate n_c symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A relation between two finite sets is stored as a Boolean matrix of relation, so the storage cost is the entry count.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for n_c:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning n_c = 19.6111 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 39.2222 — kept a factor of two that cancels in the correct rearrangement.
- 9.8056 — dropped that same factor in the other direction.
- 21.5722 — rounded an intermediate value before the final step.
Reference: FE Handbook — Discrete Mathematics (Matrix of Relation)
a relation matrix linking survey stations to control points Given rows (elements of the first set) (n_r) = 19.0000; columns (elements of the second set) (n_c) = 10.0000, determine the matrix entries (E) in entries.
Given
Find
matrix entries (E), in entries
Start with the thinking
- The governing relation printed in this handbook section is Entries in a relation (adjacency) matrix.
- Everything except E is given, so isolate E symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A relation between two finite sets is stored as a Boolean matrix of relation, so the storage cost is the entry count.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for E:
Step 3 — List the givens: rows (elements of the first set) (n_r) = 19.0000, columns (elements of the second set) (n_c) = 10.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning E = 190.0 entries to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 380.0 — kept a factor of two that cancels in the correct rearrangement.
- 95.0000 — dropped that same factor in the other direction.
- 209.0 — rounded an intermediate value before the final step.
Reference: FE Handbook — Discrete Mathematics (Matrix of Relation)
a finite state machine transition table stored as a Boolean matrix Given matrix entries (E) = 113.0 entries; columns (elements of the second set) (n_c) = 5.0000, determine the rows (elements of the first set) (n_r).
Given
Find
rows (elements of the first set) (n_r)
Start with the thinking
- The governing relation printed in this handbook section is Entries in a relation (adjacency) matrix.
- Everything except n_r is given, so isolate n_r symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A relation between two finite sets is stored as a Boolean matrix of relation, so the storage cost is the entry count.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for n_r:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning n_r = 22.6000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 45.2000 — kept a factor of two that cancels in the correct rearrangement.
- 11.3000 — dropped that same factor in the other direction.
- 24.8600 — rounded an intermediate value before the final step.
Reference: FE Handbook — Discrete Mathematics (Matrix of Relation)
a relation matrix linking pipe nodes to demand nodes Given matrix entries (E) = 346.0 entries; rows (elements of the first set) (n_r) = 16.0000, determine the columns (elements of the second set) (n_c).
Given
Find
columns (elements of the second set) (n_c)
Start with the thinking
- The governing relation printed in this handbook section is Entries in a relation (adjacency) matrix.
- Everything except n_c is given, so isolate n_c symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A relation between two finite sets is stored as a Boolean matrix of relation, so the storage cost is the entry count.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for n_c:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning n_c = 21.6250 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 43.2500 — kept a factor of two that cancels in the correct rearrangement.
- 10.8125 — dropped that same factor in the other direction.
- 23.7875 — rounded an intermediate value before the final step.
Reference: FE Handbook — Discrete Mathematics (Matrix of Relation)
a relation matrix linking survey stations to control points Given rows (elements of the first set) (n_r) = 11.0000; columns (elements of the second set) (n_c) = 4.0000, determine the matrix entries (E) in entries.
Given
Find
matrix entries (E), in entries
Start with the thinking
- The governing relation printed in this handbook section is Entries in a relation (adjacency) matrix.
- Everything except E is given, so isolate E symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A relation between two finite sets is stored as a Boolean matrix of relation, so the storage cost is the entry count.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for E:
Step 3 — List the givens: rows (elements of the first set) (n_r) = 11.0000, columns (elements of the second set) (n_c) = 4.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning E = 44.0000 entries to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 88.0000 — kept a factor of two that cancels in the correct rearrangement.
- 22.0000 — dropped that same factor in the other direction.
- 48.4000 — rounded an intermediate value before the final step.
Reference: FE Handbook — Discrete Mathematics (Matrix of Relation)
a finite state machine transition table stored as a Boolean matrix Given matrix entries (E) = 90.0000 entries; columns (elements of the second set) (n_c) = 17.0000, determine the rows (elements of the first set) (n_r).
Given
Find
rows (elements of the first set) (n_r)
Start with the thinking
- The governing relation printed in this handbook section is Entries in a relation (adjacency) matrix.
- Everything except n_r is given, so isolate n_r symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A relation between two finite sets is stored as a Boolean matrix of relation, so the storage cost is the entry count.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for n_r:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning n_r = 5.2941 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 10.5882 — kept a factor of two that cancels in the correct rearrangement.
- 2.6471 — dropped that same factor in the other direction.
- 5.8235 — rounded an intermediate value before the final step.
Reference: FE Handbook — Discrete Mathematics (Matrix of Relation)
a relation matrix linking pipe nodes to demand nodes Given matrix entries (E) = 335.0 entries; rows (elements of the first set) (n_r) = 10.0000, determine the columns (elements of the second set) (n_c).
Given
Find
columns (elements of the second set) (n_c)
Start with the thinking
- The governing relation printed in this handbook section is Entries in a relation (adjacency) matrix.
- Everything except n_c is given, so isolate n_c symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A relation between two finite sets is stored as a Boolean matrix of relation, so the storage cost is the entry count.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for n_c:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning n_c = 33.5000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 67.0000 — kept a factor of two that cancels in the correct rearrangement.
- 16.7500 — dropped that same factor in the other direction.
- 36.8500 — rounded an intermediate value before the final step.
Reference: FE Handbook — Discrete Mathematics (Matrix of Relation)
a relation matrix linking survey stations to control points Given rows (elements of the first set) (n_r) = 9.0000; columns (elements of the second set) (n_c) = 4.0000, determine the matrix entries (E) in entries.
Given
Find
matrix entries (E), in entries
Start with the thinking
- The governing relation printed in this handbook section is Entries in a relation (adjacency) matrix.
- Everything except E is given, so isolate E symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A relation between two finite sets is stored as a Boolean matrix of relation, so the storage cost is the entry count.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for E:
Step 3 — List the givens: rows (elements of the first set) (n_r) = 9.0000, columns (elements of the second set) (n_c) = 4.0000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning E = 36.0000 entries to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 72.0000 — kept a factor of two that cancels in the correct rearrangement.
- 18.0000 — dropped that same factor in the other direction.
- 39.6000 — rounded an intermediate value before the final step.
Reference: FE Handbook — Discrete Mathematics (Matrix of Relation)