$1256 \times 3892 = x$
Aptitude
Number System
Difficulty: Hard
Choose an option
-
A4883852
-
B4888532
-
C4888352
-
D4883582
-
ENone of these
Answer
Correct Answer: 4888352
Explanation
Concept & Strategy
This is a straight arithmetic question requiring the multiplication of two four-digit numbers. Breaking down one of the numbers into simpler components (distributive property) is the most reliable manual method.
Step-by-Step Solution
* We need to calculate:
$$1256 \times 3892$$
* Let's break down $3892$ into $(4000 - 100 - 8)$ for easier multiplication.
$$1256 \times (4000 - 100 - 8)$$
* Multiply $1256$ by each component:
$$1256 \times 4000 = 5024000$$
$$1256 \times 100 = 125600$$
$$1256 \times 8 = 10048$$
* Now combine them according to the signs:
$$5024000 - 125600 - 10048$$
* Subtract $125600$ from $5024000$:
$$5024000 - 125600 = 4898400$$
* Finally, subtract $10048$:
$$4898400 - 10048 = 4888352$$
Exam Strategy & Shortcut
Let's use the last two digits to eliminate options.
Multiply the last two digits of both numbers: $56 \times 92$.
$56 \times (100 - 8) = 5600 - 448 = 5152$.
The product must end in $52$. Options (a), (c), and (e) are left.
Now use the digital root (sum of digits until a single digit is reached):
Digital root of $1256 = 1+2+5+6 = 14 \rightarrow 1+4 = 5$.
Digital root of $3892 = 3+8+9+2 = 22 \rightarrow 2+2 = 4$.
Product of digital roots = $5 \times 4 = 20 \rightarrow 2+0 = 2$.
Check digital roots of remaining options:
(a) $4883852 \rightarrow 4+8+8+3+8+5+2 = 38 \rightarrow 11 \rightarrow 2$. (Possible)
(c) $4888352 \rightarrow 4+8+8+8+3+5+2 = 38 \rightarrow 11 \rightarrow 2$. (Possible)
We need to evaluate deeper. If we approximate: $1250 \times 3900 = 4875000$. Our exact number should be slightly higher. $4888352$ is a better fit than $4883852$.
Common Pitfall
Doing a standard 4-by-4 long multiplication is extremely prone to addition errors in the middle rows. Breaking it into manageable chunks reduces this risk.
Final Answer
**Therefore, the correct answer is 4888352.**