SSC CGL 2022 PYQ — Question 89

SSC CGL Tier II - Quant - 29 Jan 2022 • Quantitative Aptitude • Q89

If 22242−3+5\frac{22 \sqrt2}{4\sqrt2-\sqrt3+\sqrt5}= a + √5b, with a, b > 0, then what is the value of (ab) : (a+b)?

Show answer & explanation

Correct answer: D

Explanation

 The correct answer is option 4 i.e. 7 : 8

⇒   22242−3+5\frac{22 \sqrt2}{4\sqrt2-\sqrt3+\sqrt5}= a + √5b

On rationalizing the LHS part we get,

⇒   22242−3+5\frac{22 \sqrt2}{4\sqrt2-\sqrt3+\sqrt5}= a + √5b

⇒ 222×(42−3−5)(42−3+5)(42−3−5\frac{22 \sqrt2 \times(4\sqrt2-\sqrt3-\sqrt5)}{(4\sqrt2-\sqrt3+\sqrt5)(4\sqrt2-\sqrt3-\sqrt5}

⇒ 2(88−116−11102(15−46)\frac{2(88 - 11\sqrt6 - 11\sqrt{10}}{2(15 - 4 \sqrt6)}

Again on rationalization, we get,

⇒ (88−116−1110(15−46)×15+4615+46\frac{(88 - 11\sqrt6 - 11\sqrt{10}}{(15 - 4 \sqrt6)} \times \frac{15 + 4\sqrt6}{15 + 4\sqrt6}.