Dimensional Analysis
Calculating Dosages Safely
3rd Edition
• Author(s)Tracy Horntvedt
TEST BANK
Q1
Reference
Ch. 1 — Whole Numbers — Adding Whole Numbers
Stem
A provider orders: Give 2 tablets of acetaminophen every 6
hours for 48 hours. The supply contains 500-tablet bottles.
Using dimensional analysis, how many tablets will the nurse
administer in total over 48 hours? Show dimensional setup
mentally to confirm supply suffices.
Options
A. 8 tablets
,B. 12 tablets
C. 16 tablets
D. 24 tablets
Correct Answer
C. 16 tablets
Rationales
Correct (C): Setup: (48 hours ÷ 6 hours) = 8 doses; 8 doses × 2
tablets/dose = 16 tablets. All units cancel properly (hours →
doses → tablets). No rounding needed; supply (500 tablets) far
exceeds required amount, so safe.
A (8 tablets): Error: used number of doses (48 ÷ 6 = 8) but
forgot to multiply by tablets per dose. Common omission of
final multiplication.
B (12 tablets): Error: likely multiplied 6 doses × 2 tablets (6
instead of 8) — a misdivision error.
D (24 tablets): Error: perhaps multiplied 12 doses incorrectly
(48 ÷ 4) or used 3 tablets per dose instead of 2 — incorrect
setup.
Teaching Point
Divide hours by dosing interval → multiply by tablets per dose;
maintain unit flow.
Citation
Horntvedt, T. (3rd ed.). Dimensional Analysis: Calculating
Dosages Safely. Ch. 1.
,Q2
Reference
Ch. 1 — Whole Numbers — Subtracting Whole Numbers
Stem
Provider orders: Administer 5 mL of a pediatric suspension every
8 hours for 3 days. The pharmacy supplied a 90 mL bottle. How
many milliliters will remain in the bottle after treatment? Use
dimensional analysis steps and whole-number arithmetic.
Options
A. 50 mL remaining
B. 35 mL remaining
C. 30 mL remaining
D. 10 mL remaining
Correct Answer
B. 35 mL remaining
Rationales
Correct (B): Doses: (3 days × 24 hours/day) ÷ 8 hours = (72 ÷ 8)
= 9 doses. Total mL used: 9 × 5 mL = 45 mL. Remaining: 90 − 45
= 45 mL (Wait—check). Correction: recalc shows 90 − 45 = 45
mL — option B is 35 mL which is incorrect. (We must ensure
correct answer exists.) [Assistant correction needed:
recompute and pick correct option].
[Assistant made an arithmetic error in drafting — must fix
before finalizing; re-evaluate options so correct aligns.]
— Revised Q2 below —
, Q2 (revised)
Reference
Ch. 1 — Whole Numbers — Subtracting Whole Numbers
Stem
Provider orders: Administer 5 mL of a pediatric suspension every
8 hours for 3 days. The pharmacy supplied a 90 mL bottle. How
many milliliters will remain in the bottle after treatment? Use
dimensional analysis steps and whole-number arithmetic.
Options
A. 50 mL remaining
B. 45 mL remaining
C. 30 mL remaining
D. 10 mL remaining
Correct Answer
B. 45 mL remaining
Rationales
Correct (B): (3 days × 24 hours/day) ÷ 8 hours = 72 ÷ 8 = 9
doses. Total used = 9 × 5 mL = 45 mL. Remaining = 90 − 45 = 45
mL. Units cancelled correctly; subtraction yields whole-number
remainder.
A (50 mL): Error: miscalculated doses as 8 (8 × 5 = 40; 90 − 40 =
50) — common off-by-one in dose count.
C (30 mL): Error: total used would be 60 mL (90 − 60 = 30)
implying 12 doses or mis-interval (e.g., every 6 hours), wrong
setup.
Calculating Dosages Safely
3rd Edition
• Author(s)Tracy Horntvedt
TEST BANK
Q1
Reference
Ch. 1 — Whole Numbers — Adding Whole Numbers
Stem
A provider orders: Give 2 tablets of acetaminophen every 6
hours for 48 hours. The supply contains 500-tablet bottles.
Using dimensional analysis, how many tablets will the nurse
administer in total over 48 hours? Show dimensional setup
mentally to confirm supply suffices.
Options
A. 8 tablets
,B. 12 tablets
C. 16 tablets
D. 24 tablets
Correct Answer
C. 16 tablets
Rationales
Correct (C): Setup: (48 hours ÷ 6 hours) = 8 doses; 8 doses × 2
tablets/dose = 16 tablets. All units cancel properly (hours →
doses → tablets). No rounding needed; supply (500 tablets) far
exceeds required amount, so safe.
A (8 tablets): Error: used number of doses (48 ÷ 6 = 8) but
forgot to multiply by tablets per dose. Common omission of
final multiplication.
B (12 tablets): Error: likely multiplied 6 doses × 2 tablets (6
instead of 8) — a misdivision error.
D (24 tablets): Error: perhaps multiplied 12 doses incorrectly
(48 ÷ 4) or used 3 tablets per dose instead of 2 — incorrect
setup.
Teaching Point
Divide hours by dosing interval → multiply by tablets per dose;
maintain unit flow.
Citation
Horntvedt, T. (3rd ed.). Dimensional Analysis: Calculating
Dosages Safely. Ch. 1.
,Q2
Reference
Ch. 1 — Whole Numbers — Subtracting Whole Numbers
Stem
Provider orders: Administer 5 mL of a pediatric suspension every
8 hours for 3 days. The pharmacy supplied a 90 mL bottle. How
many milliliters will remain in the bottle after treatment? Use
dimensional analysis steps and whole-number arithmetic.
Options
A. 50 mL remaining
B. 35 mL remaining
C. 30 mL remaining
D. 10 mL remaining
Correct Answer
B. 35 mL remaining
Rationales
Correct (B): Doses: (3 days × 24 hours/day) ÷ 8 hours = (72 ÷ 8)
= 9 doses. Total mL used: 9 × 5 mL = 45 mL. Remaining: 90 − 45
= 45 mL (Wait—check). Correction: recalc shows 90 − 45 = 45
mL — option B is 35 mL which is incorrect. (We must ensure
correct answer exists.) [Assistant correction needed:
recompute and pick correct option].
[Assistant made an arithmetic error in drafting — must fix
before finalizing; re-evaluate options so correct aligns.]
— Revised Q2 below —
, Q2 (revised)
Reference
Ch. 1 — Whole Numbers — Subtracting Whole Numbers
Stem
Provider orders: Administer 5 mL of a pediatric suspension every
8 hours for 3 days. The pharmacy supplied a 90 mL bottle. How
many milliliters will remain in the bottle after treatment? Use
dimensional analysis steps and whole-number arithmetic.
Options
A. 50 mL remaining
B. 45 mL remaining
C. 30 mL remaining
D. 10 mL remaining
Correct Answer
B. 45 mL remaining
Rationales
Correct (B): (3 days × 24 hours/day) ÷ 8 hours = 72 ÷ 8 = 9
doses. Total used = 9 × 5 mL = 45 mL. Remaining = 90 − 45 = 45
mL. Units cancelled correctly; subtraction yields whole-number
remainder.
A (50 mL): Error: miscalculated doses as 8 (8 × 5 = 40; 90 − 40 =
50) — common off-by-one in dose count.
C (30 mL): Error: total used would be 60 mL (90 − 60 = 30)
implying 12 doses or mis-interval (e.g., every 6 hours), wrong
setup.
