HENKE'S MED-MATH
DOSAGE CALCULATION, PREPARATION
& ADMINISTRATION
10TH EDITION
• AUTHOR(S)SUSAN BUCHHOLZ
TEST BANK
1
Reference
Ch. 1 — Multiplying Whole Numbers
Stem
A physician orders amoxicillin 20 mg/kg PO single dose for a
child weighing 15 kg. The medication supplied is amoxicillin
suspension 250 mg per 5 mL. How many mL should the nurse
give?
Options
A. 4 mL
B. 6 mL
,C. 3 mL
D. 12 mL
Correct answer
B. 6 mL
Rationales
Correct (B): Calculate total dose: 20 mg/kg × 15 kg = 300 mg.
Use the concentration ratio: 250 mg : 5 mL = 300 mg : x mL → x
= 300 × (5/250) = 300 × 0.02 = 6 mL. Give 6 mL.
A (4 mL): Error likely from dividing weight by concentration or
using 15×(5/250) without the mg/kg factor; underdoses the
patient.
C (3 mL): Represents halving the correct volume (300 × (5/500)
error) — incorrect conversion of concentration.
D (12 mL): Likely doubling the correct result (misplaced
decimal), which would overdose.
Teaching point
Multiply mg/kg first; then convert using the concentration ratio.
Citation
Buchholz, S. (2024). Henke’s Med-Math: Dosage Calculation,
Preparation & Administration (10th ed.). Ch. 1.
2
Reference
Ch. 1 — Dividing Whole Numbers
,Stem
A provider prescribes 450 mg of medication. Tablets available
are 150 mg each. How many tablets should the nurse
administer?
Options
A. 2 tablets
B. 3 tablets
C. 4 tablets
D. 1.5 tablets
Correct answer
B. 3 tablets
Rationales
Correct (B): Divide total ordered dose by tablet strength: 450
mg ÷ 150 mg/tablet = 3 tablets.
A (2 tablets): Underestimates—equates to 300 mg total (450 →
300 mg), likely from subtracting instead of dividing.
C (4 tablets): Would give 600 mg; common error is rounding up
without calculation.
D (1.5 tablets): Suggests dividing by 300 mg/tablet (incorrect
assumed tablet strength) or mixing units — unsafe and
incorrect.
Teaching point
Always divide total ordered dose by single-tablet strength;
check units cancel.
, Citation
Buchholz, S. (2024). Henke’s Med-Math… Ch. 1.
3
Reference
Ch. 1 — Fractions
Stem
An order calls for three-quarters (¾) of a 400 mg tablet (patient
refusal requires pill splitting). How many milligrams of active
drug will the patient receive?
Options
A. 100 mg
B. 200 mg
C. 300 mg
D. 400 mg
Correct answer
C. 300 mg
Rationales
Correct (C): Multiply the fraction by tablet strength: ¾ × 400 mg
= 0.75 × 400 = 300 mg.
A (100 mg): Reflects ¼ of the tablet, not ¾; common fraction
inversion error.
B (200 mg): Reflects ½ of the tablet; error from misreading ¾ as
½.
D (400 mg): Full tablet—ignores instructed fraction.
DOSAGE CALCULATION, PREPARATION
& ADMINISTRATION
10TH EDITION
• AUTHOR(S)SUSAN BUCHHOLZ
TEST BANK
1
Reference
Ch. 1 — Multiplying Whole Numbers
Stem
A physician orders amoxicillin 20 mg/kg PO single dose for a
child weighing 15 kg. The medication supplied is amoxicillin
suspension 250 mg per 5 mL. How many mL should the nurse
give?
Options
A. 4 mL
B. 6 mL
,C. 3 mL
D. 12 mL
Correct answer
B. 6 mL
Rationales
Correct (B): Calculate total dose: 20 mg/kg × 15 kg = 300 mg.
Use the concentration ratio: 250 mg : 5 mL = 300 mg : x mL → x
= 300 × (5/250) = 300 × 0.02 = 6 mL. Give 6 mL.
A (4 mL): Error likely from dividing weight by concentration or
using 15×(5/250) without the mg/kg factor; underdoses the
patient.
C (3 mL): Represents halving the correct volume (300 × (5/500)
error) — incorrect conversion of concentration.
D (12 mL): Likely doubling the correct result (misplaced
decimal), which would overdose.
Teaching point
Multiply mg/kg first; then convert using the concentration ratio.
Citation
Buchholz, S. (2024). Henke’s Med-Math: Dosage Calculation,
Preparation & Administration (10th ed.). Ch. 1.
2
Reference
Ch. 1 — Dividing Whole Numbers
,Stem
A provider prescribes 450 mg of medication. Tablets available
are 150 mg each. How many tablets should the nurse
administer?
Options
A. 2 tablets
B. 3 tablets
C. 4 tablets
D. 1.5 tablets
Correct answer
B. 3 tablets
Rationales
Correct (B): Divide total ordered dose by tablet strength: 450
mg ÷ 150 mg/tablet = 3 tablets.
A (2 tablets): Underestimates—equates to 300 mg total (450 →
300 mg), likely from subtracting instead of dividing.
C (4 tablets): Would give 600 mg; common error is rounding up
without calculation.
D (1.5 tablets): Suggests dividing by 300 mg/tablet (incorrect
assumed tablet strength) or mixing units — unsafe and
incorrect.
Teaching point
Always divide total ordered dose by single-tablet strength;
check units cancel.
, Citation
Buchholz, S. (2024). Henke’s Med-Math… Ch. 1.
3
Reference
Ch. 1 — Fractions
Stem
An order calls for three-quarters (¾) of a 400 mg tablet (patient
refusal requires pill splitting). How many milligrams of active
drug will the patient receive?
Options
A. 100 mg
B. 200 mg
C. 300 mg
D. 400 mg
Correct answer
C. 300 mg
Rationales
Correct (C): Multiply the fraction by tablet strength: ¾ × 400 mg
= 0.75 × 400 = 300 mg.
A (100 mg): Reflects ¼ of the tablet, not ¾; common fraction
inversion error.
B (200 mg): Reflects ½ of the tablet; error from misreading ¾ as
½.
D (400 mg): Full tablet—ignores instructed fraction.
