TEST BANK BASED ON:
Calculating Drug Dosages
A Patient-Safe Approach to Nursing and Math
3rd Edition
• Author(s)Sandra Luz Martinez de Castillo;
Maryanne Werner-McCullough
Chapter 1 — Section: Units & Conversions — Safety in
Medication Administration
Stem: The order reads: give 2,500 mcg of a medication. The vial
label reads 1 mg per mL. How many mL should the nurse
administer?
A. 0.25 mL
B. 2.5 mL
C. 25 mL
D. 1.25 mL
Correct Answer: B
Rationales:
• Correct (B): Convert micrograms to milligrams: 2,500 mcg
= 2,500 ÷ 1,000 = 2.5 mg. Vial: 1 mg = 1 mL → 2.5 mg = 2.5
, mL. Stepwise: 2,500 mcg → 2,500 ÷ 1,000 = 2.5 mg → 2.5
mg × (1 mL / 1 mg) = 2.5 mL.
• (A) 0.25 mL — decimal point error (moved decimal left one
place; reflects dividing by 10 instead of 1,000).
• (C) 25 mL — factor-of-10 error (moved decimal right
instead of left).
• (D) 1.25 mL — half of correct dose; reflects a halving error
or miscalculation when converting.
Teaching Point: Always convert units completely before using
concentration to calculate volume.
2.
Chapter 1 — Section: Tablet Dosage & Rounding — Safety in
Medication Administration
Stem: Order: 75 mg oral of Drug X. Available: scored tablets of
25 mg. How many tablets should be given?
A. 2 tablets
B. 2.5 tablets
C. 3 tablets
D. 4 tablets
Correct Answer: C
Rationales:
, • Correct (C): 75 mg ÷ 25 mg per tablet = 3 tablets exactly.
Step: 75 ÷ 25 = 3.
• (A) 2 tablets — underdose; reflects subtraction or division
error (2 × 25 = 50 mg).
• (B) 2.5 tablets — wrong; 2.5 × 25 = 62.5 mg, not 75 mg
(misapplies half-tablet when not needed).
• (D) 4 tablets — overdose (4 × 25 = 100 mg); reflects
rounding up incorrectly.
Teaching Point: Perform exact division first; use scored tablets
only when math requires halves.
3.
Chapter 1 — Section: Pediatric Weight-Based Dosing — Safety
in Medication Administration
Stem: A child weighs 22 lb. Provider orders ampicillin 75
mg/kg/day divided q8h. Available concentration/dose forms
allow 250 mg per dose (1 mL = 250 mg). What volume (mL) is
given per dose?
A. 0.5 mL
B. 1.0 mL
C. 1.0 mL (250 mg per dose)
D. 2.0 mL
Correct Answer: C
Rationales:
, • Correct (C): Convert weight to kg: 22 lb ÷ 2.2 = 10.0 kg.
Total daily dose = 75 mg/kg × 10.0 kg = 750 mg/day.
Divided q8h = 3 doses/day → per dose = 750 mg ÷ 3 = 250
mg. Available: 250 mg = 1.0 mL. Stepwise: 22 ÷ 2.2 = 10 kg
→ 75 × 10 = 750 mg/day → 750 ÷ 3 = 250 mg/dose → 250
mg × (1 mL / 250 mg) = 1.0 mL.
• (A) 0.5 mL — half the needed volume (125 mg); reflects
halving error.
• (B) 1.0 mL — same number as C but presented without the
explanation; C clarifies mg. (B effectively similar but C is
correctly labeled).
• (D) 2.0 mL — double the correct volume (500 mg); reflects
doubling error.
Teaching Point: Convert weight to kg before any mg/kg
calculation.
4.
Chapter 1 — Section: IV Drip Calculations (gtt/min) — Safety in
Medication Administration
Stem: Infuse 1,000 mL normal saline over 8 hours using tubing
calibrated 15 gtt/mL. What is the infusion rate in drops per
minute (gtt/min)? (Round to nearest whole drop.)
A. 30 gtt/min
B. 31 gtt/min
Calculating Drug Dosages
A Patient-Safe Approach to Nursing and Math
3rd Edition
• Author(s)Sandra Luz Martinez de Castillo;
Maryanne Werner-McCullough
Chapter 1 — Section: Units & Conversions — Safety in
Medication Administration
Stem: The order reads: give 2,500 mcg of a medication. The vial
label reads 1 mg per mL. How many mL should the nurse
administer?
A. 0.25 mL
B. 2.5 mL
C. 25 mL
D. 1.25 mL
Correct Answer: B
Rationales:
• Correct (B): Convert micrograms to milligrams: 2,500 mcg
= 2,500 ÷ 1,000 = 2.5 mg. Vial: 1 mg = 1 mL → 2.5 mg = 2.5
, mL. Stepwise: 2,500 mcg → 2,500 ÷ 1,000 = 2.5 mg → 2.5
mg × (1 mL / 1 mg) = 2.5 mL.
• (A) 0.25 mL — decimal point error (moved decimal left one
place; reflects dividing by 10 instead of 1,000).
• (C) 25 mL — factor-of-10 error (moved decimal right
instead of left).
• (D) 1.25 mL — half of correct dose; reflects a halving error
or miscalculation when converting.
Teaching Point: Always convert units completely before using
concentration to calculate volume.
2.
Chapter 1 — Section: Tablet Dosage & Rounding — Safety in
Medication Administration
Stem: Order: 75 mg oral of Drug X. Available: scored tablets of
25 mg. How many tablets should be given?
A. 2 tablets
B. 2.5 tablets
C. 3 tablets
D. 4 tablets
Correct Answer: C
Rationales:
, • Correct (C): 75 mg ÷ 25 mg per tablet = 3 tablets exactly.
Step: 75 ÷ 25 = 3.
• (A) 2 tablets — underdose; reflects subtraction or division
error (2 × 25 = 50 mg).
• (B) 2.5 tablets — wrong; 2.5 × 25 = 62.5 mg, not 75 mg
(misapplies half-tablet when not needed).
• (D) 4 tablets — overdose (4 × 25 = 100 mg); reflects
rounding up incorrectly.
Teaching Point: Perform exact division first; use scored tablets
only when math requires halves.
3.
Chapter 1 — Section: Pediatric Weight-Based Dosing — Safety
in Medication Administration
Stem: A child weighs 22 lb. Provider orders ampicillin 75
mg/kg/day divided q8h. Available concentration/dose forms
allow 250 mg per dose (1 mL = 250 mg). What volume (mL) is
given per dose?
A. 0.5 mL
B. 1.0 mL
C. 1.0 mL (250 mg per dose)
D. 2.0 mL
Correct Answer: C
Rationales:
, • Correct (C): Convert weight to kg: 22 lb ÷ 2.2 = 10.0 kg.
Total daily dose = 75 mg/kg × 10.0 kg = 750 mg/day.
Divided q8h = 3 doses/day → per dose = 750 mg ÷ 3 = 250
mg. Available: 250 mg = 1.0 mL. Stepwise: 22 ÷ 2.2 = 10 kg
→ 75 × 10 = 750 mg/day → 750 ÷ 3 = 250 mg/dose → 250
mg × (1 mL / 250 mg) = 1.0 mL.
• (A) 0.5 mL — half the needed volume (125 mg); reflects
halving error.
• (B) 1.0 mL — same number as C but presented without the
explanation; C clarifies mg. (B effectively similar but C is
correctly labeled).
• (D) 2.0 mL — double the correct volume (500 mg); reflects
doubling error.
Teaching Point: Convert weight to kg before any mg/kg
calculation.
4.
Chapter 1 — Section: IV Drip Calculations (gtt/min) — Safety in
Medication Administration
Stem: Infuse 1,000 mL normal saline over 8 hours using tubing
calibrated 15 gtt/mL. What is the infusion rate in drops per
minute (gtt/min)? (Round to nearest whole drop.)
A. 30 gtt/min
B. 31 gtt/min
