Given that $\sqrt{3} = 1.732$, the value of $$ \frac{3 + \sqrt{6}}{5\sqrt{3} - 2\sqrt{12} - \sqrt{32} + \sqrt{50}} $$ is
Aptitude
Square Root and Cube Root
Difficulty: Medium
Choose an option
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A1.414
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B1.732
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C2.551
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D4.899
Answer
Correct Answer: 1.732
Explanation
### Concept & Formula
The core strategy is simplifying compound surds by extracting perfect square factors from inside the square roots.
Use the property:
$$ \sqrt{a^2 \times b} = a\sqrt{b} $$
After breaking down all terms into their simplest radical forms, combine like terms to simplify the fraction.
### Step-by-Step Solution
Let's simplify the numerator and denominator separately.
**Numerator:**
$3 + \sqrt{6}$
We can extract a common factor of $\sqrt{3}$ because $3 = (\sqrt{3})^2$ and $\sqrt{6} = \sqrt{3}\sqrt{2}$:
Numerator $= \sqrt{3}(\sqrt{3} + \sqrt{2})$
**Denominator:**
$5\sqrt{3} - 2\sqrt{12} - \sqrt{32} + \sqrt{50}$
Simplify each term by factoring out perfect squares:
$\sqrt{12} = \sqrt{4 \times 3} = 2\sqrt{3}$
$\sqrt{32} = \sqrt{16 \times 2} = 4\sqrt{2}$
$\sqrt{50} = \sqrt{25 \times 2} = 5\sqrt{2}$
Substitute these back into the denominator:
$= 5\sqrt{3} - 2(2\sqrt{3}) - 4\sqrt{2} + 5\sqrt{2}$
$= 5\sqrt{3} - 4\sqrt{3} - 4\sqrt{2} + 5\sqrt{2}$
Group the like terms (the $\sqrt{3}$ terms together and the $\sqrt{2}$ terms together):
$= (5 - 4)\sqrt{3} + (5 - 4)\sqrt{2}$
$= \sqrt{3} + \sqrt{2}$
**Recombine Fraction:**
Expression $= \frac{\sqrt{3}(\sqrt{3} + \sqrt{2})}{\sqrt{3} + \sqrt{2}}$
The term $(\sqrt{3} + \sqrt{2})$ cancels out from the top and bottom:
Expression $= \sqrt{3}$
Substitute the given value $\sqrt{3} = 1.732$.
### Exam Strategy & Shortcut
In competitive exams, complicated-looking surd fractions almost always simplify down to a single radical term. Once you spot that the denominator simplifies to $\sqrt{3} + \sqrt{2}$, look at the numerator $3 + \sqrt{6}$. Recognize instantly that $\sqrt{3}$ is a multiplier that maps the denominator to the numerator. Cancel them mentally to arrive at $\sqrt{3}$ directly.
### Common Pitfall
A major trap is attempting to plug in $1.732$ for $\sqrt{3}$ and approximating other roots like $\sqrt{2}$ at the very beginning. This creates a nightmare of decimal arithmetic that wastes time and guarantees calculation errors. Always simplify variables and radicals fully before substituting numeric values.
### Final Answer
**Therefore, the correct answer is 1.732.**