TEST BANK FOR CALCULATION OF DRUG
DOSAGES, 12TH EDITION BY SHEILA J. OGDEN
AND LINDA FLUHARTY |ALL CHAPTERS |
QUESTIONS AND ANSWERS WITH RATIONALES
LATEST
,CHAPTER 1 — FRACTIONS
1. Convert the fraction 3/8 to a decimal and a percent.
Answer: Decimal = 0.375; Percent = 37.5%
Rationale: Divide numerator by denominator: 3 ÷ 8 = 0.375 (do long
division: 8 into 30 → 3 remainder 6 → 8 into 60 → 7 remainder 4 → 8 into
40 → 5 → stops). To convert decimal to percent, multiply by 100: 0.375 ×
100 = 37.5%.
2. A medication order calls for 5/16 of a grain per dose. Express 5/16 as a
decimal (to three decimal places) and then multiply by 2 to find the dose
for two administrations.
Answer: 5/16 = 0.3125 → per dose; two doses = 0.625 (or 5/8).
Rationale: 5 ÷ 16 = 0.3125. Doubling: 0.3125 × 2 = 0.625. Optionally
reduce: 0.625 = 5/8.
3. A drug vial contains 7/12 mL of concentrate. If a nurse must give 1/4 of
the vial, how many milliliters will be administered?
Answer: (7/12) × (1/4) = 7/48 mL ≈ 0.1458 mL.
Rationale: Multiply fractions: 7××4 = 7/48. For decimal: 7 ÷ 48 =
0.145833..., round as needed.
4. Reduce the fraction 84/126 to lowest terms.
Answer: 2/3.
Rationale: Compute GCD: 84 and 126 are both divisible by 42 → 84 ÷ 42 =
2, 126 ÷ 42 = 3 → 2/3.
5. A pediatric dose is 1 3/4 teaspoons. Convert to an improper fraction and
then to milliliters (1 tsp = 5 mL).
Answer: 1 3/4 = 7/4 tsp; 7/4 × 5 mL = 35/4 mL = 8.75 mL.
, Rationale: Mixed → improper: 1×4 + 3 = 7 → 7/4 tsp. Multiply by 5
mL/tsp → 35/4 = 8.75 mL.
6. If a solution is prepared by mixing 2/5 L of solvent with 3/10 L of solute,
what fraction of the total volume is solute?
Answer: Total = 2/5 + 3/10 = 4/10 + 3/10 = 7/10 L; Solute fraction = (3/10)
÷ (7/10) = 3/7 ≈ 0.4286 (42.86%).
Rationale: Add volumes; fraction of solute = solute/total; dividing fractions
cancels denominators.
7. A stock concentration is 3/16 mg/mL. How many milligrams are in 5
mL?
Answer: (3/16 mg/mL) × 5 mL = 15/16 mg = 0.9375 mg.
Rationale: Multiply: 3× = 15/16.
8. A prescription requires 7/9 of a tablet; each tablet is scored in halves
(i.e., 1/2 increments). Is it possible to give exactly 7/9 with the available
scoring? If not, choose the closest practical fraction and state the
difference in tablet fraction.
Answer: 7/9 ≈ 0.777...; half increments: possible fractions are 1/2 = 0.5, 1 =
1.0, 3/4 = 0.75 (but 3/4 requires quarter scoring not available), with half
increments only you can give 1/2 (0.5) or 1 (1.0); nearest is 1 tablet
(difference 2/9 ≈ 0.222) or 1/2 tablet (difference ≈ 0.2778). If tablets are
scored into halves only, you cannot give 7/9 exactly; you'd choose nearest
and document.
Rationale: Compare decimal equivalents; discuss clinical decision-making.
, 9. Add: 5/12 + 7/18. Give answer in simplest form.
Answer: LCD = 36: (15/36 + 14/36) = 29/36.
Rationale: Convert to common denominator and add; 29/36 is irreducible.
10.Subtract: 11/20 − 2/5.
Answer: 11/20 − 8/20 = 3/20.
Rationale: Convert 2/5 to 8/20, subtract.
11.Multiply: (4/7) × (21/16). Simplify fully.
Answer: Cancel 21 with 7: 21/7 = 3 → (4 × 3) / 16 = 12/16 = 3/4.
Rationale: Cancel common factors before multiplying to simplify.
12.Divide: (9/10) ÷ (3/5).
Answer: (9/10) × (5/3) = (9×5)/(10×3) → cancel 9 & 3 → 3× = 15/10
= 3/2 = 1 1/2.
Rationale: Division becomes multiply by reciprocal; reduce along the way.
13.A drug order is for 2/3 of a 30 mg tablet. How many milligrams will the
patient get?
Answer: 2/3 × 30 mg = 20 mg.
Rationale: Multiply numerator by mg then divide by denominator
(2×30/3=60/3=20).
14.Express 0.625 as a fraction in lowest terms.
Answer: 0.625 = 625/1000 = divide by 125 → 5/8.
Rationale: Convert decimal to fraction and reduce.
15.A pharmacist prepares a 1/20 dilution of a drug. If the final volume
required is 200 mL, how much stock solution is needed?
Answer: 1/20 of 200 mL = 200/20 = 10 mL stock + 190 mL diluent.
Rationale: Multiply fraction by total volume.
DOSAGES, 12TH EDITION BY SHEILA J. OGDEN
AND LINDA FLUHARTY |ALL CHAPTERS |
QUESTIONS AND ANSWERS WITH RATIONALES
LATEST
,CHAPTER 1 — FRACTIONS
1. Convert the fraction 3/8 to a decimal and a percent.
Answer: Decimal = 0.375; Percent = 37.5%
Rationale: Divide numerator by denominator: 3 ÷ 8 = 0.375 (do long
division: 8 into 30 → 3 remainder 6 → 8 into 60 → 7 remainder 4 → 8 into
40 → 5 → stops). To convert decimal to percent, multiply by 100: 0.375 ×
100 = 37.5%.
2. A medication order calls for 5/16 of a grain per dose. Express 5/16 as a
decimal (to three decimal places) and then multiply by 2 to find the dose
for two administrations.
Answer: 5/16 = 0.3125 → per dose; two doses = 0.625 (or 5/8).
Rationale: 5 ÷ 16 = 0.3125. Doubling: 0.3125 × 2 = 0.625. Optionally
reduce: 0.625 = 5/8.
3. A drug vial contains 7/12 mL of concentrate. If a nurse must give 1/4 of
the vial, how many milliliters will be administered?
Answer: (7/12) × (1/4) = 7/48 mL ≈ 0.1458 mL.
Rationale: Multiply fractions: 7××4 = 7/48. For decimal: 7 ÷ 48 =
0.145833..., round as needed.
4. Reduce the fraction 84/126 to lowest terms.
Answer: 2/3.
Rationale: Compute GCD: 84 and 126 are both divisible by 42 → 84 ÷ 42 =
2, 126 ÷ 42 = 3 → 2/3.
5. A pediatric dose is 1 3/4 teaspoons. Convert to an improper fraction and
then to milliliters (1 tsp = 5 mL).
Answer: 1 3/4 = 7/4 tsp; 7/4 × 5 mL = 35/4 mL = 8.75 mL.
, Rationale: Mixed → improper: 1×4 + 3 = 7 → 7/4 tsp. Multiply by 5
mL/tsp → 35/4 = 8.75 mL.
6. If a solution is prepared by mixing 2/5 L of solvent with 3/10 L of solute,
what fraction of the total volume is solute?
Answer: Total = 2/5 + 3/10 = 4/10 + 3/10 = 7/10 L; Solute fraction = (3/10)
÷ (7/10) = 3/7 ≈ 0.4286 (42.86%).
Rationale: Add volumes; fraction of solute = solute/total; dividing fractions
cancels denominators.
7. A stock concentration is 3/16 mg/mL. How many milligrams are in 5
mL?
Answer: (3/16 mg/mL) × 5 mL = 15/16 mg = 0.9375 mg.
Rationale: Multiply: 3× = 15/16.
8. A prescription requires 7/9 of a tablet; each tablet is scored in halves
(i.e., 1/2 increments). Is it possible to give exactly 7/9 with the available
scoring? If not, choose the closest practical fraction and state the
difference in tablet fraction.
Answer: 7/9 ≈ 0.777...; half increments: possible fractions are 1/2 = 0.5, 1 =
1.0, 3/4 = 0.75 (but 3/4 requires quarter scoring not available), with half
increments only you can give 1/2 (0.5) or 1 (1.0); nearest is 1 tablet
(difference 2/9 ≈ 0.222) or 1/2 tablet (difference ≈ 0.2778). If tablets are
scored into halves only, you cannot give 7/9 exactly; you'd choose nearest
and document.
Rationale: Compare decimal equivalents; discuss clinical decision-making.
, 9. Add: 5/12 + 7/18. Give answer in simplest form.
Answer: LCD = 36: (15/36 + 14/36) = 29/36.
Rationale: Convert to common denominator and add; 29/36 is irreducible.
10.Subtract: 11/20 − 2/5.
Answer: 11/20 − 8/20 = 3/20.
Rationale: Convert 2/5 to 8/20, subtract.
11.Multiply: (4/7) × (21/16). Simplify fully.
Answer: Cancel 21 with 7: 21/7 = 3 → (4 × 3) / 16 = 12/16 = 3/4.
Rationale: Cancel common factors before multiplying to simplify.
12.Divide: (9/10) ÷ (3/5).
Answer: (9/10) × (5/3) = (9×5)/(10×3) → cancel 9 & 3 → 3× = 15/10
= 3/2 = 1 1/2.
Rationale: Division becomes multiply by reciprocal; reduce along the way.
13.A drug order is for 2/3 of a 30 mg tablet. How many milligrams will the
patient get?
Answer: 2/3 × 30 mg = 20 mg.
Rationale: Multiply numerator by mg then divide by denominator
(2×30/3=60/3=20).
14.Express 0.625 as a fraction in lowest terms.
Answer: 0.625 = 625/1000 = divide by 125 → 5/8.
Rationale: Convert decimal to fraction and reduce.
15.A pharmacist prepares a 1/20 dilution of a drug. If the final volume
required is 200 mL, how much stock solution is needed?
Answer: 1/20 of 200 mL = 200/20 = 10 mL stock + 190 mL diluent.
Rationale: Multiply fraction by total volume.
