Variances
Construction Engineering · 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 construction engineering problem uses Crew productivity. Given production rate (P) = 41.0000 units/hr; duration (t) = 120.0 hr, determine the total quantity (Q) in units.
Given
Find
total quantity (Q), in units
Start with the thinking
- The governing relation printed in this handbook section is Crew productivity.
- Everything except Q is given, so isolate Q 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.
- Construction Engineering items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that Q stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Q = 4,920 units to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 9,840 — kept a factor of two that cancels in the correct rearrangement.
- 2,460 — dropped that same factor in the other direction.
- 5,412 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Construction Engineering → Variances
A construction engineering problem uses Total cost from unit cost. Given unit cost (cu) = 96.5000 $/unit; quantity (Q) = 3,603 units, determine the total cost (C) in $.
Given
unit cost (cu) = 96.5000 $/unit
Find
total cost (C), in $
Start with the thinking
- The governing relation printed in this handbook section is Total cost from unit cost.
- Everything except C is given, so isolate 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.
- Construction Engineering items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that C stands alone on the left-hand side.
Step 3 — List the givens: unit cost (cu) = 96.5000 $/unit, quantity (Q) = 3,603 units.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning C = 347,690 $ to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 695,379 — kept a factor of two that cancels in the correct rearrangement.
- 173,845 — dropped that same factor in the other direction.
- 382,458 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Construction Engineering → Variances
earned value cost performance index for a highway construction contract Given earned value (BCWP) (EV) = 247,500 $; actual cost (ACWP) (AC) = 440,000 $; cost variance (CV) = 85,500 $, determine the cost performance index (CPI).
Given
earned value (BCWP) (EV) = 247,500 $
actual cost (ACWP) (AC) = 440,000 $
cost variance (CV) = 85,500 $
Find
cost performance index (CPI)
Start with the thinking
- The governing relation printed in this handbook section is Earned value: cost performance index and cost variance.
- Everything except CPI is given, so isolate CPI 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.
- Earned value management measures project cost performance and productivity using cost performance index and cost variance.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that CPI stands alone on the left-hand side.
Step 3 — List the givens: earned value (BCWP) (EV) = 247,500 $, actual cost (ACWP) (AC) = 440,000 $, cost variance (CV) = 85,500 $.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning CPI = 0.5625 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.1250 — kept a factor of two that cancels in the correct rearrangement.
- 0.2813 — dropped that same factor in the other direction.
- 0.6188 — rounded an intermediate value before the final step.
Reference: FE Handbook — Nomenclature (earned value / productivity)
A construction engineering problem uses Crew productivity. Given duration (t) = 185.0 hr; total quantity (Q) = 1,706 units, determine the production rate (P) in units/hr.
Given
Find
production rate (P), in units/hr
Start with the thinking
- The governing relation printed in this handbook section is Crew productivity.
- Everything except P is given, so isolate P 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.
- Construction Engineering items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that P stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning P = 9.2216 units/hr to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 18.4432 — kept a factor of two that cancels in the correct rearrangement.
- 4.6108 — dropped that same factor in the other direction.
- 10.1438 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Construction Engineering → Variances
A construction engineering problem uses Total cost from unit cost. Given quantity (Q) = 762.0 units; total cost (C) = 148,123 $, determine the unit cost (cu) in $/unit.
Given
total cost (C) = 148,123 $
Find
unit cost (cu), in $/unit
Start with the thinking
- The governing relation printed in this handbook section is Total cost from unit cost.
- Everything except cu is given, so isolate cu 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.
- Construction Engineering items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that cu stands alone on the left-hand side.
Step 3 — List the givens: quantity (Q) = 762.0 units, total cost (C) = 148,123 $.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning cu = 194.4 $/unit to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 388.8 — kept a factor of two that cancels in the correct rearrangement.
- 97.1936 — dropped that same factor in the other direction.
- 213.8 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Construction Engineering → Variances
earned value analysis to assess cost performance on a construction project Given earned value (BCWP) (EV) = 82,000 $; actual cost (ACWP) (AC) = 416,500 $; cost performance index (CPI) = 1.3600, determine the cost variance (CV) in $.
Given
earned value (BCWP) (EV) = 82,000 $
actual cost (ACWP) (AC) = 416,500 $
Find
cost variance (CV), in $
Start with the thinking
- The governing relation printed in this handbook section is Earned value: cost performance index and cost variance.
- Everything except CV is given, so isolate CV 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.
- Earned value management measures project cost performance and productivity using cost performance index and cost variance.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that CV stands alone on the left-hand side.
Step 3 — List the givens: earned value (BCWP) (EV) = 82,000 $, actual cost (ACWP) (AC) = 416,500 $, cost performance index (CPI) = 1.3600.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning CV = -334,500 $ to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -669,000 — kept a factor of two that cancels in the correct rearrangement.
- -167,250 — dropped that same factor in the other direction.
- -367,950 — rounded an intermediate value before the final step.
Reference: FE Handbook — Nomenclature (earned value / productivity)
A construction engineering problem uses Crew productivity. Given production rate (P) = 71.0000 units/hr; total quantity (Q) = 3,710 units, determine the duration (t) in hr.
Given
Find
duration (t), in hr
Start with the thinking
- The governing relation printed in this handbook section is Crew productivity.
- Everything except t is given, so isolate t 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.
- Construction Engineering items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that t stands alone on the left-hand side.
Step 3 — List the givens: production rate (P) = 71.0000 units/hr, total quantity (Q) = 3,710 units.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning t = 52.2535 hr to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 104.5 — kept a factor of two that cancels in the correct rearrangement.
- 26.1268 — dropped that same factor in the other direction.
- 57.4789 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Construction Engineering → Variances
A construction engineering problem uses Total cost from unit cost. Given unit cost (cu) = 274.0 $/unit; total cost (C) = 195,376 $, determine the quantity (Q) in units.
Given
unit cost (cu) = 274.0 $/unit
total cost (C) = 195,376 $
Find
quantity (Q), in units
Start with the thinking
- The governing relation printed in this handbook section is Total cost from unit cost.
- Everything except Q is given, so isolate Q 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.
- Construction Engineering items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that Q stands alone on the left-hand side.
Step 3 — List the givens: unit cost (cu) = 274.0 $/unit, total cost (C) = 195,376 $.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Q = 713.1 units to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1,426 — kept a factor of two that cancels in the correct rearrangement.
- 356.5 — dropped that same factor in the other direction.
- 784.4 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Construction Engineering → Variances
productivity and cost variance tracking on a building project schedule Given earned value (BCWP) (EV) = 323,500 $; cost performance index (CPI) = 0.7100; cost variance (CV) = 69,500 $, determine the actual cost (ACWP) (AC) in $.
Given
earned value (BCWP) (EV) = 323,500 $
cost variance (CV) = 69,500 $
Find
actual cost (ACWP) (AC), in $
Start with the thinking
- The governing relation printed in this handbook section is Earned value: cost performance index and cost variance.
- Everything except AC is given, so isolate AC 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.
- Earned value management measures project cost performance and productivity using cost performance index and cost variance.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that AC stands alone on the left-hand side.
Step 3 — List the givens: earned value (BCWP) (EV) = 323,500 $, cost performance index (CPI) = 0.7100, cost variance (CV) = 69,500 $.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning AC = 455,634 $ to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 911,268 — kept a factor of two that cancels in the correct rearrangement.
- 227,817 — dropped that same factor in the other direction.
- 501,197 — rounded an intermediate value before the final step.
Reference: FE Handbook — Nomenclature (earned value / productivity)
A construction engineering problem uses Crew productivity. Given production rate (P) = 59.0000 units/hr; duration (t) = 29.0000 hr, determine the total quantity (Q) in units.
Given
Find
total quantity (Q), in units
Start with the thinking
- The governing relation printed in this handbook section is Crew productivity.
- Everything except Q is given, so isolate Q 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.
- Construction Engineering items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that Q stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Q = 1,711 units to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3,422 — kept a factor of two that cancels in the correct rearrangement.
- 855.5 — dropped that same factor in the other direction.
- 1,882 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Construction Engineering → Variances