Dimensional Analysis
Calculating Dosages Safely
3rd Edition
• Author(s)Tracy Horntvedt
TEST BANK
1
Reference: Ch. 1 — Whole Numbers — Multiplying Whole
Numbers
Clinical stem: The provider orders acetaminophen 1,500 mg PO
now. The medication on hand is 500 mg scored tablets. Using
dimensional analysis, how many tablets should the nurse
administer?
A. 2 tablets
B. 3 tablets
,C. 4 tablets
D. 5 tablets
Correct answer: B. 3 tablets
Rationale — Correct (B):
Dimensional analysis:
1500 mg×1 tablet500 mg=3 tablets.1500\,\text{mg} \times
\frac{1\ \text{tablet}}{500\,\text{mg}} = 3\
\text{tablets}.1500mg×500mg1 tablet=3 tablets. Units cancel
(mg→tablet). Multiplication/division of whole numbers yields
an exact whole tablet. This is safe and matches scored-tablet
practice.
Rationale — Incorrect:
A: (2 tablets) results from dividing 1500 by 750 (arithmetic
error) — underdose.
C: (4 tablets) comes from 1500 ÷ 375 (misapplied divisor) —
overdose.
D: (5 tablets) reflects 1500 ÷ 300 (wrong strength) — unsafe
overdose.
Teaching point: Always set up mg → tablet as a fraction to
cancel mg units cleanly.
Citation: Horntvedt, T. (3rd ed.). Dimensional Analysis:
Calculating Dosages Safely. Ch. 1.
2
,Reference: Ch. 1 — Whole Numbers — Dividing Whole
Numbers
Clinical stem: The physician orders heparin 2,000 units IV. Vials
are labeled 1,000 units/mL. Using dimensional analysis, how
many milliliters should the nurse draw up?
A. 1 mL
B. 2 mL
C. 3 mL
D. 4 mL
Correct answer: B. 2 mL
Rationale — Correct (B):
Dimensional analysis:
2000 units×1 mL1000 units=2 mL.2000\,\text{units} \times
\frac{1\,\text{mL}}{1000\,\text{units}} =
2\,\text{mL}.2000units×1000units1mL=2mL. Units cancel
(units→mL). Division of whole numbers yields an exact whole
mL.
Rationale — Incorrect:
A: (1 mL) is from treating vial as 2000 units/mL — underdose.
C: (3 mL) from 2000 ÷ 667 (incorrect conversion) — overdose.
D: (4 mL) from misreading vial as 500 units/mL — large
overdose.
Teaching point: Align the unit ratio (units per mL) to cancel
units precisely.
, Citation: Horntvedt, T. (3rd ed.). Dimensional Analysis:
Calculating Dosages Safely. Ch. 1.
3
Reference: Ch. 1 — Whole Numbers — Dividing Whole
Numbers
Clinical stem: An IV infusion order reads 1,200 mL NS over 12
hours. The pump requires mL/hr. Using dimensional analysis,
what rate should the nurse program?
A. 90 mL/hr
B. 100 mL/hr
C. 110 mL/hr
D. 120 mL/hr
Correct answer: B. 100 mL/hr
Rationale — Correct (B):
Dimensional analysis:
1200 mL÷12 hr=100 mL/hr.1200\,\text{mL} \div 12\,\text{hr} =
100\,\text{mL/hr}.1200mL÷12hr=100mL/hr. Units cancel
(mL/hr). Division of whole numbers gives exact whole mL/hr;
pump programmable.
Rationale — Incorrect:
A: (90) likely from dividing by 13.3 — arithmetic slip.
C: (110) from rounding 1000/9 — calculation error.
D: (120) from misreading time as 10 hr — unsafe faster infusion.
Calculating Dosages Safely
3rd Edition
• Author(s)Tracy Horntvedt
TEST BANK
1
Reference: Ch. 1 — Whole Numbers — Multiplying Whole
Numbers
Clinical stem: The provider orders acetaminophen 1,500 mg PO
now. The medication on hand is 500 mg scored tablets. Using
dimensional analysis, how many tablets should the nurse
administer?
A. 2 tablets
B. 3 tablets
,C. 4 tablets
D. 5 tablets
Correct answer: B. 3 tablets
Rationale — Correct (B):
Dimensional analysis:
1500 mg×1 tablet500 mg=3 tablets.1500\,\text{mg} \times
\frac{1\ \text{tablet}}{500\,\text{mg}} = 3\
\text{tablets}.1500mg×500mg1 tablet=3 tablets. Units cancel
(mg→tablet). Multiplication/division of whole numbers yields
an exact whole tablet. This is safe and matches scored-tablet
practice.
Rationale — Incorrect:
A: (2 tablets) results from dividing 1500 by 750 (arithmetic
error) — underdose.
C: (4 tablets) comes from 1500 ÷ 375 (misapplied divisor) —
overdose.
D: (5 tablets) reflects 1500 ÷ 300 (wrong strength) — unsafe
overdose.
Teaching point: Always set up mg → tablet as a fraction to
cancel mg units cleanly.
Citation: Horntvedt, T. (3rd ed.). Dimensional Analysis:
Calculating Dosages Safely. Ch. 1.
2
,Reference: Ch. 1 — Whole Numbers — Dividing Whole
Numbers
Clinical stem: The physician orders heparin 2,000 units IV. Vials
are labeled 1,000 units/mL. Using dimensional analysis, how
many milliliters should the nurse draw up?
A. 1 mL
B. 2 mL
C. 3 mL
D. 4 mL
Correct answer: B. 2 mL
Rationale — Correct (B):
Dimensional analysis:
2000 units×1 mL1000 units=2 mL.2000\,\text{units} \times
\frac{1\,\text{mL}}{1000\,\text{units}} =
2\,\text{mL}.2000units×1000units1mL=2mL. Units cancel
(units→mL). Division of whole numbers yields an exact whole
mL.
Rationale — Incorrect:
A: (1 mL) is from treating vial as 2000 units/mL — underdose.
C: (3 mL) from 2000 ÷ 667 (incorrect conversion) — overdose.
D: (4 mL) from misreading vial as 500 units/mL — large
overdose.
Teaching point: Align the unit ratio (units per mL) to cancel
units precisely.
, Citation: Horntvedt, T. (3rd ed.). Dimensional Analysis:
Calculating Dosages Safely. Ch. 1.
3
Reference: Ch. 1 — Whole Numbers — Dividing Whole
Numbers
Clinical stem: An IV infusion order reads 1,200 mL NS over 12
hours. The pump requires mL/hr. Using dimensional analysis,
what rate should the nurse program?
A. 90 mL/hr
B. 100 mL/hr
C. 110 mL/hr
D. 120 mL/hr
Correct answer: B. 100 mL/hr
Rationale — Correct (B):
Dimensional analysis:
1200 mL÷12 hr=100 mL/hr.1200\,\text{mL} \div 12\,\text{hr} =
100\,\text{mL/hr}.1200mL÷12hr=100mL/hr. Units cancel
(mL/hr). Division of whole numbers gives exact whole mL/hr;
pump programmable.
Rationale — Incorrect:
A: (90) likely from dividing by 13.3 — arithmetic slip.
C: (110) from rounding 1000/9 — calculation error.
D: (120) from misreading time as 10 hr — unsafe faster infusion.
