$2056 \times 987 = x$
Aptitude
Number System
Difficulty: Medium
Choose an option
-
A1936372
-
B2029272
-
C1896172
-
D1923472
-
ENone of these
Answer
Correct Answer: 2029272
Explanation
### Concept & Formula
When a multiplier is close to a thousand (like 987), we can express it as 1000 minus a small integer to use the distributive property, significantly simplifying the math.
$$a \times (b - c) = ab - ac$$
### Step-by-Step Solution
* Express 987 as $1000 - 13$:
$$2056 \times 987 = 2056 \times (1000 - 13)$$
* Distribute the multiplication:
$$(2056 \times 1000) - (2056 \times 13)$$
* Calculate the two parts:
$$2056000 - 26728$$
* Perform the final subtraction:
$$2056000 - 26728 = 2029272$$
### Exam Strategy & Shortcut
Use the last two digits to eliminate options!
The last two digits of the answer will be the last two digits of $56 \times 87$.
$56 \times 87 \rightarrow 56 \times (100 - 13) = 5600 - 728 = 4872$.
The last two digits are 72. All options have 72!
Expand to the last three digits: $056 \times 987$.
$056 \times (1000 - 13) = 56000 - 728 = 55272$.
The last three digits must be 272. Only options (b) and (d) end in 272.
Estimate: $2000 \times 1000 = 2000000$. The exact answer will be close to this, making 2029272 the logical choice over 1923472.
### Common Pitfall
Attempting a three-by-four digit standard multiplication line by line. This takes at least triple the time and introduces a high probability of simple addition errors in the final sum.
### Final Answer
**Therefore, the correct answer is 2029272.**