SSC Selection Post 2020 PYQ — Question 67

The correct answer is Option 1 i.e. 12.

(20 – x), (37 – x), (54 – x), (105 – x) are in proportion.

⇒ (20 – x)/(37 – x) = (54 – x)/(105 – x)

⇒ 2100 – 125x + x² = 1998 – 91x + x²

⇒ 2100 – 125x = 1998 – 91x

⇒ 102 = 34x

⇒ x = 3

mean proportion between (7x – 5) and (x + 1) = $\sqrt{(7x – 5) (x + 1)}$

= $\sqrt{(21 – 5) (3 + 1)}$

= $\sqrt{64}$ = 8