The sum of two number is 37 and the difference of their squares is 185, then the difference between the two numbers is:
Aptitude
Problems on Numbers
Difficulty: Easy
Choose an option
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A10
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B4
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C5
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D3
Answer
Correct Answer: 5
Explanation
Concept & Formula
Utilize the standard algebraic identity for the difference of squares to relate the sum, difference, and squares of two numbers.
$$ x^2 - y^2 = (x - y)(x + y) $$
Step-by-Step Solution
* **Given:** Let the two numbers be $x$ and $y$. Sum $x + y = 37$. Difference of squares $x^2 - y^2 = 185$.
* **Calculation:** Expand the difference of squares identity:
$x^2 - y^2 = (x - y)(x + y)$
* Substitute the known values into the equation:
$185 = (x - y)(37)$
* Solve for the difference $(x - y)$:
$x - y = 185 / 37$
* Divide 185 by 37:
$x - y = 5$
Exam Strategy & Shortcut
**Direct Formula Application:** Recognize instantly that $(x^2 - y^2) / (x + y) = (x - y)$. Simply divide the difference of the squares by the sum of the numbers to get the difference of the numbers. $185 / 37 = 5$. This takes 5 seconds and requires no paper.
Common Pitfall
Students sometimes try to solve for $x$ and $y$ individually by creating a quadratic equation or guessing numbers. This wastes immense time when the identity directly yields the required difference.
Final Answer
**Therefore, the correct answer is 5.**