Alligation method MCQs With Answer

Alligation Method MCQs With Answer — a must-know topic in B. Pharm pharmacy calculations. The alligation method (alligation alternate and alligation medial) helps pharmacists quickly compute mixing ratios and amounts for solutions, mixtures, and ointments of different strengths. Mastering this tool supports practical compounding tasks like dilution, fortification, cost blending, and converting between percentage strength, ratio strength (1 in x), and w/v, w/w, v/v units. These MCQs focus on concentration targets, cross-differences, feasibility checks (desired strength within range), and real-world problems (alcohol, dextrose, ointments, purity adjustments). Learn to use parts as relative quantities, choose correct units, and avoid common pitfalls. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which statement best describes the alligation alternate method?

• A method to convert w/w to w/v using specific gravity
• A graphical tool to find median concentration of multiple solutions
• A rule to find the mixing ratio of two concentrations to achieve a desired concentration
• A method for calculating isotonicity adjustments using E-values

Correct Answer: A rule to find the mixing ratio of two concentrations to achieve a desired concentration

Q2. Alligation medial is primarily used to determine:

• The weighted average strength of a mixture from known quantities and strengths
• The minimum volume of solvent needed for complete dissolution
• The molar concentration of a buffered system
• The precipitation threshold of a solute

Correct Answer: The weighted average strength of a mixture from known quantities and strengths

Q3. What is the mixing ratio (20% solution : 50% solution) to obtain 30% w/v using alligation?

• 1:2
• 2:1
• 3:1
• 1:3

Correct Answer: 2:1

Q4. How many milliliters of 90% v/v alcohol are needed with water to prepare 1000 mL of 70% v/v alcohol?

• 700 mL
• 750 mL
• 778 mL
• 833 mL

Correct Answer: 778 mL

Q5. To prepare 15% w/v by mixing 25% and 10% solutions, the ratio (25% : 10%) is:

• 1:2
• 2:1
• 3:2
• 5:3

Correct Answer: 1:2

Q6. You have 80% pure drug and pure (100%) drug. In what ratio should they be mixed to obtain 90% potency?

• 1:2
• 2:1
• 1:1
• 3:1

Correct Answer: 1:1

Q7. How many grams of 95% w/w acid are required to make 500 g of 60% w/w acid by mixing with a 30% w/w solution?

• 200.0 g
• 230.8 g
• 269.2 g
• 300.0 g

Correct Answer: 230.8 g

Q8. Find the mixing ratio (95% alcohol : 40% alcohol) to prepare 70% v/v alcohol.

• 5:6
• 6:5
• 2:1
• 3:2

Correct Answer: 6:5

Q9. How many milliliters of 10% w/v stock are needed to prepare 1000 mL of a 1 in 1000 (w/v) solution?

• 1 mL
• 10 mL
• 25 mL
• 100 mL

Correct Answer: 10 mL

Q10. Which desired strength cannot be obtained by mixing 10% and 20% solutions?

• 12%
• 15%
• 18%
• 25%

Correct Answer: 25%

Q11. Equal volumes of a 20% solution and an x% solution yield a 30% solution. What is x?

• 35%
• 40%
• 45%
• 60%

Correct Answer: 40%

Q12. How many grams of pure drug are needed to fortify 500 g of 8% w/w ointment to 10% w/w?

• 5.00 g
• 10.00 g
• 11.11 g
• 12.50 g

Correct Answer: 11.11 g

Q13. What volume of 80% v/v alcohol is needed, with water, to prepare 500 mL of 30% v/v alcohol?

• 150 mL
• 175 mL
• 187.5 mL
• 200 mL

Correct Answer: 187.5 mL

Q14. What is the mixing ratio (1:20 solution : 1:200 solution) to obtain a 1:50 solution?

• 2:1
• 1:2
• 3:1
• 1:3

Correct Answer: 1:2

Q15. What is the first step when solving by alligation alternate?

• Convert all concentrations to molarity
• Place the strengths of the two components at the left-hand corners
• Cross-multiply final and initial volumes
• Compute specific gravity corrections

Correct Answer: Place the strengths of the two components at the left-hand corners

Q16. Which combination is valid for alligation without unit conversion?

• 20% w/v with 5 g/100 mL for a desired % w/v product
• 10% w/w with 10% v/v for a desired % w/v product
• 1 in 1000 (w/v) with 5% v/v for a desired % v/v product
• 25 mg/mL with 70% v/v for a desired % w/w product

Correct Answer: 20% w/v with 5 g/100 mL for a desired % w/v product

Q17. How much of a 60% w/w ointment is required, with 25% w/w ointment, to make 1 kg of 40% w/w?

• 350 g
• 400 g
• 428.6 g
• 500.0 g

Correct Answer: 428.6 g

Q18. What volume of 10% w/v solution is needed to mix with 100 mL of 40% w/v to obtain 25% w/v?

• 50 mL
• 75 mL
• 100 mL
• 150 mL

Correct Answer: 100 mL

Q19. If 200 mL of 20% w/v is mixed with 300 mL of 50% w/v, what is the final strength (% w/v)?

• 32%
• 35%
• 38%
• 40%

Correct Answer: 38%

Q20. To prepare 250 mL of 12% w/v from 8% and 20% w/v solutions, what volume of the 20% solution is required?

• 62.5 mL
• 75.0 mL
• 83.33 mL
• 100.0 mL

Correct Answer: 83.33 mL

Q21. Grade A alcohol costs $8/L and Grade B costs $14/L. What is the mixing ratio (A : B) to obtain a $10/L blend?

• 1:1
• 1:2
• 2:1
• 3:1

Correct Answer: 2:1

Q22. Alligation alternate can be iteratively applied to more than two components as long as the desired strength lies within the range of extremes.

• True
• False
• Only for liquids
• Only if the parts sum to 1

Correct Answer: True

Q23. Determine the mixing ratio (20% solution : 1% solution) to obtain a 5% solution.

• 3:1
• 1:3
• 4:15
• 15:4

Correct Answer: 15:4

Q24. How many milliliters of 25% w/v dextrose are needed to prepare 1000 mL of 10% w/v using a 5% w/v solution for dilution?

• 150 mL
• 200 mL
• 250 mL
• 300 mL

Correct Answer: 250 mL

Q25. In alligation, “parts” represent:

• Absolute grams or milliliters to measure directly
• Relative quantities proportional to the required amounts
• Molar fractions that always sum to 1
• The number of molecules in each solution

Correct Answer: Relative quantities proportional to the required amounts

Q26. What volume of 10% w/v solution is required to prepare 250 mL of 2% w/v using water as diluent?

• 25 mL
• 40 mL
• 50 mL
• 75 mL

Correct Answer: 50 mL

Q27. If 3 parts of a 30% solution are mixed with 2 parts of a 10% solution, the final concentration is:

• 18%
• 20%
• 22%
• 24%

Correct Answer: 22%

Q28. Which statement about the cross-difference rule in alligation alternate is correct?

• The quantity of each component is proportional to the difference between the desired concentration and its own concentration
• The quantity of each component is proportional to the difference between the desired concentration and the other component’s concentration
• Differences are added to find the final volume
• Differences are squared to improve accuracy

Correct Answer: The quantity of each component is proportional to the difference between the desired concentration and the other component’s concentration

Q29. What is the ratio (1:1000 solution : water) needed to make a 1:2500 (w/v) solution?

• 1:1
• 2:3
• 3:2
• 1:2

Correct Answer: 2:3

Q30. The minimum number of components required to apply alligation alternate is:

• 1
• 2
• 3
• 4

Correct Answer: 2

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