$x \times (|a| \times |b|) = -ab$
Aptitude
Number System
Difficulty: Medium
Choose an option
-
A0
-
B-1
-
C1
-
DNone of these
Answer
Correct Answer: None of these
Explanation
Concept & Logic
This algebraic question deals with the properties of absolute values. The absolute value of a product is equal to the product of their absolute values: $|a| \times |b| = |ab|$.
Step-by-Step Solution
* Simplify the given equation:
$$x \times (|a| \times |b|) = -ab$$
$$x \times |ab| = -ab$$
* Isolate $x$:
$$x = \frac{-ab}{|ab|}$$
* The value of $x$ depends entirely on the sign of the product $ab$:
* Case 1: If $a$ and $b$ have the SAME sign (both positive or both negative), then $ab > 0$. Therefore, $|ab| = ab$.
$$x = \frac{-ab}{ab} = -1$$
* Case 2: If $a$ and $b$ have OPPOSITE signs (one positive, one negative), then $ab < 0$. Therefore, $|ab| = -ab$.
$$x = \frac{-ab}{-ab} = 1$$
* Since the value of $x$ is not a single constant and changes based on the signs of $a$ and $b$, neither $1$ nor $-1$ is universally correct.
Exam Strategy & Shortcut
Whenever dealing with absolute values equal to variables without specified domains (e.g., $a,b > 0$), expect multiple cases. Since $x$ can evaluate to either $1$ or $-1$ depending on the integers chosen, a single definitive numeric option is impossible. Instantly choose "None of these".
Common Pitfall
Assuming that variables $a$ and $b$ are strictly positive integers. If you make this assumption, you will erroneously conclude that $x = -1$ and select option (b).
Final Answer
**Therefore, the correct answer is None of these.**