Practice Questions
Concept Explanation
Percentage concentration expresses parts of solute per 100 parts of solution. It links directly to mixture and alligation when prices represent concentration values.
Key Formulas
- Percentage concentration = (solute / total solution) × 100
- Alligation applies: mix p1% and p2% to get pm%
- Ratio = (p2 − pm) : (pm − p1)
Example
Mix 20% and 50% solutions to get 35%. Ratio = (50 − 35) : (35 − 20) = 15 : 15 = 1 : 1.
Common Trap
Percentage is of total solution, not of solvent alone.
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Q1 Easy
Mix 20% and 50% solutions for 35%. Ratio is:
Explanation(50 − 35) : (35 − 20) = 15 : 15 = 1 : 1. -
Q2 Easy
10% and 30% solutions mixed equally. Final concentration is:
ExplanationEqual mix: (10 + 30)/2 = 20%. -
Q3 Easy
25% and 45% for 35%. Ratio lower : higher is:
Explanation(45 − 35) : (35 − 25) = 10 : 10 = 1 : 1. -
Q4 Medium
40 L of 15% and 60 L of 25%. Final concentration is:
ExplanationSolute = 6 + 15 = 21 in 100 L = 21%. -
Q5 Medium
5% and 35% for 20%. Ratio lower : higher is:
Explanation(35 − 20) : (20 − 5) = 15 : 15 = 1 : 1. -
Q6 Medium
30 L of 8% and 70 L of 18%. Final concentration is:
ExplanationSolute = 2.4 + 12.6 = 15 in 100 L = 15%. -
Q7 Easy
12% and 28% for 20%. Ratio lower : higher is:
Explanation(28 − 20) : (20 − 12) = 8 : 8 = 1 : 1.
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Q8 Hard
20% and 40% for 30%. In 80 L mixture, volume of 40% solution is:
ExplanationRatio = 1 : 1. Higher 40% share = 80/2 = 40 L. -
Q9 Medium
15% and 45% for 30%. Ratio lower : higher is:
Explanation(45 − 30) : (30 − 15) = 15 : 15 = 1 : 1. -
Q10 Easy
50 L of 6% and 50 L of 14%. Final concentration is:
ExplanationEqual volumes: (6 + 14)/2 = 10%. -
Q11 Medium
18% and 42% for 30%. Ratio lower : higher is:
Explanation(42 − 30) : (30 − 18) = 12 : 12 = 1 : 1. -
Q12 Medium
24 L of 10% and 36 L of 30%. Final concentration is:
ExplanationSolute = 2.4 + 10.8 = 13.2 in 60 L = 22%. -
Q13 Hard
Which pair gives 25% when mixed 1 : 1?
ExplanationOption B: (15 + 35)/2 = 25%. -
Q14 Hard
8% and 32% for 20%. Ratio lower : higher is:
Explanation(32 − 20) : (20 − 8) = 12 : 12 = 1 : 1.
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DS1 Easy
What is the final concentration?
Statement I20% and 50% solutions are mixed 1 : 1.
Statement IIEqual volumes of 20% and 50% are mixed.
ExplanationEach gives (20 + 50)/2 = 35%. -
DS2 Medium
What is the mixing ratio?
Statement I10% and 30% solutions give 20%.
Statement IILower and higher concentrations differ by 20 percentage points.
ExplanationStatement I alone: ratio = 1 : 1.
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DS3 Medium
Is final concentration 21%?
Statement I40 L of 15% and 60 L of 25% are mixed.
Statement II30 L of 8% and 70 L of 18% are mixed.
ExplanationI gives 21%. II gives 15%. -
DS4 Hard
How much 40% solution is in the mix?
Statement I20% and 40% give 30% in ratio 1 : 1.
Statement IITotal mixture is 80 litres.
ExplanationNeed both: 40% share = 40 L.