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SSC Selection Post 2022 PYQ — Question 70

SSC Selection Post - Matriculation Level 2022 - 7 Feb 2022 - Shift 2 • Quantitative Aptitude • Q70

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When x is subtracted from each of the numbers 64, 81, 85, and 109, the numbers obtained in this order are in proportion. What is the main proportion between (x + 3) and (2x - 1)?

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Correct answer: D

Explanation

The correct answer is option 4 i.e. 20.

According to the question,

⇒ (64−x)(81−x)=(85−x)(109−x){(64-x)\over(81-x)}={({85-x})\over({109-x})}

⇒ (64 - x)(109 - x) = (85 - x)(81 - x)

⇒ 6976 - 64x - 109x + x2 = 6885 - 85x - 81x + x2

⇒ 6976 - 64x - 109x = 6885 - 85x - 81x

⇒ 7x = 91

⇒ x = 13

Required mean proportion = (13+3)(26−1)\sqrt{(13+3)(26-1)} 

⇒ 16×25\sqrt{16\times25} = 4 × 5 = 20