CAT 2025 Slot 1 QA Question 20

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CAT 2025 Slot 1QAAlgebra • Linear EquationEasy
Stocks A, B and C are priced at rupees 120, 90 and 150 per share, respectively. A trader holds a portfolio consisting of 10 shares of stock A, and 20 shares of stocks B and C put together. If the total value of her portfolio is rupees 3300, then the number of shares of stock B that she holds, is
TITA Answer:
Answer and solution

Answer: 15

📌 Core Concept
We are given a system of linear equations based on the total number of shares and their respective values. The governing formula is:
Total Value=(Number of Shares×Price per Share) for each stock\text{Total Value} = (\text{Number of Shares} \times \text{Price per Share}) \text{ for each stock}
🔢 Step-by-Step Solution
1
Calculate the value of stock A:
Number of shares of A = 10
Price per share of A = 120
Value of A = 10 × 120 = 1200$ rupees
2
Set up equations for stocks B and C:
Let xx be the number of shares of B.
Let yy be the number of shares of C.
Total shares of B and C: x+y=20x + y = 20
Total value of B and C: 90x+150y=210090x + 150y = 2100 (since total portfolio is 3300 and value of A is 1200)
3
Express yy in terms of xx:
y=20−xy = 20 - x
4
Substitute yy into the value equation:
90x+150(20−x)=210090x + 150(20 - x) = 2100
Expand: 90x+3000−150x=210090x + 3000 - 150x = 2100
Combine like terms: - 60x + 3000 = 2100$
Solve for xx: - 60x = -900 ⇒ x = 15$
⚡ 30-Second Shortcut
Since the total shares of B and C are 20, and the total value is 2100, the average price per share is 105.
Stock B is 90, which is 15 less than 105, and stock C is 150, which is 45 more than 105.
Let the number of B shares be xx. The total deviation is - 15x + 45(20 - x) = 0$.
Simplify: - 15x + 900 - 45x = 0 ⇒ -60x = -900 ⇒ x = 15$.
🎯 Final Answer
Correct Answer: 15

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