Question 65

Logical Reasoning Aptitude Easy

A two digit number is such that the product of its digits is 12. If 36 is added to the number, the digits interchange their places. What is the number?

(A) 38
(B) 25
(C) 24
(D) 26
โœ“ Correct Answer: Option D Verified Solution

๐Ÿ“˜ Step-by-Step Solution & Detailed Explanation:

\[ \textbf{Step 1: Let the two-digit number be } 10x + y, \] where \(x\) is the tens digit and \(y\) is the units digit. \[ \textbf{Step 2: Condition 1: Product of digits } \Rightarrow x \cdot y = 12. \] \[ \textbf{Step 3: Condition 2: Adding 36 reverses the digits } \Rightarrow 10x + y + 36 = 10y + x. \] \[ \textbf{Step 4: Simplify equation 2:} \] \[ 10x + y + 36 = 10y + x \quad \Rightarrow \quad 9x - 9y = -36 \quad \Rightarrow \quad x - y = -4. \] \[ \therefore x = y - 4. \] \[ \textbf{Step 5: Use condition 1: } x \cdot y = 12. \] \[ (y - 4)\cdot y = 12 \quad \Rightarrow \quad y^2 - 4y - 12 = 0. \] \[ \textbf{Step 6: Solve quadratic: } y = \frac{4 \pm \sqrt{16 + 48}}{2} = \frac{4 \pm 8}{2}. \] \[ y = 6 \quad \text{or} \quad y = -2 \ (\text{not possible since digit}). \] \[ \textbf{Step 7: If } y = 6, \quad x = y - 4 = 2. \] \[ \textbf{Final Answer: } \boxed{26} \]

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