IBPS PO General Awareness: Mixtures and Alligation questions with solutions

Q1. There are two types of pulses are ₹150 per kg and ₹100 per kg. In what ratio these pulses are mixed so that the mixture sold at ₹121 kg to earn a profit of 10%.

1. 2:3
2. 3:2
3. 1:2
4. 2:1

Answer: 3:2

SP = ₹121, profit = 10%, so CP = 121/1.1 = ₹110. Alligation: ratio of ₹100 pulse to ₹150 pulse = (150-110):(110-100) = 40:10 = 4:1. So ₹100 type : ₹150 type = 4:1, i.e., ₹150 type : ₹100 type = 1:4. Note: none of the given options correctly match the calculated ratio of 1:4. The answer marked '3:2' appears to contain an error in the source material.

Q2. Two iodine liquids cost ₹30 per 100 ml and ₹10 per 100 ml. The first contains 30% iodine and the second contains 10% iodine. Find the cost of 5 L of a mixture containing 17% iodine.

1. ₹750
2. ₹850
3. ₹1,020
4. ₹1,190

Answer: ₹850

Using alligation, the ratio of 30% and 10% liquids for a 17% mixture is 7:13. The cost per 100 ml becomes \((7\times 30 + 13\times 10)/20 = 17\) rupees. For 5 L = 50 units of 100 ml, total cost is 50 × 17 = ₹850.

Q3. A solution of 'gulab sharbat' has 15% sugar. Another solution has 5% sugar. How many liters of the second solution must be added to 20 liters of the first solution to make a solution of 10% sugar?

1. 5 L
2. 15 L
3. 25 L
4. 20 L

Answer: 20 L

In 20 liters of 15% solution, sugar = 3 liters. Let x liters of 5% solution be added; then total sugar becomes 3 + 0.05x and total volume becomes 20 + x. Since the final concentration is 10%, we get (3 + 0.05x)/(20 + x) = 0.10, which gives x = 20 liters.