Dimensional Analysis
Calculating Dosages Safely
3rd Edition
• Author(s)Tracy Horntvedt
TEST BANK
1)
Reference: Ch. 1 — Whole Numbers — Adding Whole Numbers
/ Tablets
Stem: A provider orders 600 mg of an oral antibiotic PO. The
nurse has 300 mg tablets on hand. Using dimensional analysis,
how many tablets should the nurse administer?
Options:
A. 1 tablet
B. 2 tablets
C. 3 tablets
D. 4 tablets
,Correct Answer: B. 2 tablets
Rationale — Correct (B):
600 mg × (1 tablet / 300 mg) = 600 ÷ 300 = 2 tablets. Unit mg
cancels, leaving tablets. The result is a whole number; no
rounding required. This meets safe dosing because the ordered
600 mg is delivered exactly.
Rationale — Incorrect:
A. (1 tablet) implies 300 mg given — underdosing due to halving
the ratio.
C. (3 tablets) results from (600 ÷ 200) error or adding an extra
tablet; unsafe overdose (900 mg).
D. (4 tablets) reflects multiplication error (300×4=1200 mg) —
large overdose.
Teaching point: Always set up factor-label so unwanted units
cancel; check final unit matches order.
Citation: Horntvedt, T. (3rd ed.). Ch. 1.
2)
Reference: Ch. 1 — Whole Numbers — Dividing Whole
Numbers / IV mL per hour
Stem: Order: 1,200 mL IV fluid to infuse over 8 hours. What
infusion rate in mL/hr should the nurse program on the pump?
(Use whole-number arithmetic.)
Options:
A. 140 mL/hr
,B. 150 mL/hr
C. 160 mL/hr
D. 175 mL/hr
Correct Answer: B. 150 mL/hr
Rationale — Correct (B):
1,200 mL ÷ 8 hr = 150 mL/hr. Setup: 1,200 mL × (1 hr / 8 hr)
cancels hours. Result is whole number and exact for pump
programming.
Rationale — Incorrect:
A. 140 mL/hr likely from 1,120 ÷ 8 misdivision.
C. 160 mL/hr from arithmetic error (1,280 ÷ 8).
D. 175 mL/hr from incorrect divisor (1,400 ÷ 8) — unsafe
deviation from order.
Teaching point: Divide total volume by whole hours first;
double-check unit cancellation.
Citation: Horntvedt, T. (3rd ed.). Ch. 1.
3)
Reference: Ch. 1 — Whole Numbers — Multiplying Whole
Numbers / Weight-based dose → mL
Stem: A child weighing 18 kg is prescribed 10 mg/kg PO. The
available suspension is 100 mg per 5 mL. Using dimensional
analysis, what volume (mL) should the nurse administer?
Options:
, A. 6 mL
B. 8 mL
C. 9 mL
D. 12 mL
Correct Answer: C. 9 mL
Rationale — Correct (C):
Dose = 10 mg/kg × 18 kg = 180 mg. Concentration: 100 mg / 5
mL → factor = 5 mL / 100 mg. Volume = 180 mg × (5 mL / 100
mg) = (180×5) ÷100 = 900 ÷100 = 9 mL. Units cancel properly.
Whole-number result; safe.
Rationale — Incorrect:
A. 6 mL suggests undercalculation (e.g., 120 mg used).
B. 8 mL suggests mis-application of concentration (perhaps 20
mg/mL mistaken).
D. 12 mL reflects adding 3 mL erroneously (overdose).
Teaching point: Multiply weight × mg/kg first; then convert mg
→ mL with concentration factor.
Citation: Horntvedt, T. (3rd ed.). Ch. 1.
4)
Reference: Ch. 1 — Whole Numbers — Subtracting Whole
Numbers / Tablet supply check
Stem: Provider orders 4 tablets of a medication stat. The nurse
has one bottle containing 24 tablets; prior doses this shift used
Calculating Dosages Safely
3rd Edition
• Author(s)Tracy Horntvedt
TEST BANK
1)
Reference: Ch. 1 — Whole Numbers — Adding Whole Numbers
/ Tablets
Stem: A provider orders 600 mg of an oral antibiotic PO. The
nurse has 300 mg tablets on hand. Using dimensional analysis,
how many tablets should the nurse administer?
Options:
A. 1 tablet
B. 2 tablets
C. 3 tablets
D. 4 tablets
,Correct Answer: B. 2 tablets
Rationale — Correct (B):
600 mg × (1 tablet / 300 mg) = 600 ÷ 300 = 2 tablets. Unit mg
cancels, leaving tablets. The result is a whole number; no
rounding required. This meets safe dosing because the ordered
600 mg is delivered exactly.
Rationale — Incorrect:
A. (1 tablet) implies 300 mg given — underdosing due to halving
the ratio.
C. (3 tablets) results from (600 ÷ 200) error or adding an extra
tablet; unsafe overdose (900 mg).
D. (4 tablets) reflects multiplication error (300×4=1200 mg) —
large overdose.
Teaching point: Always set up factor-label so unwanted units
cancel; check final unit matches order.
Citation: Horntvedt, T. (3rd ed.). Ch. 1.
2)
Reference: Ch. 1 — Whole Numbers — Dividing Whole
Numbers / IV mL per hour
Stem: Order: 1,200 mL IV fluid to infuse over 8 hours. What
infusion rate in mL/hr should the nurse program on the pump?
(Use whole-number arithmetic.)
Options:
A. 140 mL/hr
,B. 150 mL/hr
C. 160 mL/hr
D. 175 mL/hr
Correct Answer: B. 150 mL/hr
Rationale — Correct (B):
1,200 mL ÷ 8 hr = 150 mL/hr. Setup: 1,200 mL × (1 hr / 8 hr)
cancels hours. Result is whole number and exact for pump
programming.
Rationale — Incorrect:
A. 140 mL/hr likely from 1,120 ÷ 8 misdivision.
C. 160 mL/hr from arithmetic error (1,280 ÷ 8).
D. 175 mL/hr from incorrect divisor (1,400 ÷ 8) — unsafe
deviation from order.
Teaching point: Divide total volume by whole hours first;
double-check unit cancellation.
Citation: Horntvedt, T. (3rd ed.). Ch. 1.
3)
Reference: Ch. 1 — Whole Numbers — Multiplying Whole
Numbers / Weight-based dose → mL
Stem: A child weighing 18 kg is prescribed 10 mg/kg PO. The
available suspension is 100 mg per 5 mL. Using dimensional
analysis, what volume (mL) should the nurse administer?
Options:
, A. 6 mL
B. 8 mL
C. 9 mL
D. 12 mL
Correct Answer: C. 9 mL
Rationale — Correct (C):
Dose = 10 mg/kg × 18 kg = 180 mg. Concentration: 100 mg / 5
mL → factor = 5 mL / 100 mg. Volume = 180 mg × (5 mL / 100
mg) = (180×5) ÷100 = 900 ÷100 = 9 mL. Units cancel properly.
Whole-number result; safe.
Rationale — Incorrect:
A. 6 mL suggests undercalculation (e.g., 120 mg used).
B. 8 mL suggests mis-application of concentration (perhaps 20
mg/mL mistaken).
D. 12 mL reflects adding 3 mL erroneously (overdose).
Teaching point: Multiply weight × mg/kg first; then convert mg
→ mL with concentration factor.
Citation: Horntvedt, T. (3rd ed.). Ch. 1.
4)
Reference: Ch. 1 — Whole Numbers — Subtracting Whole
Numbers / Tablet supply check
Stem: Provider orders 4 tablets of a medication stat. The nurse
has one bottle containing 24 tablets; prior doses this shift used
