The mean proportional between (3 + √(5) ) and (15 - √(125) ) is ___.

SSC Selection Post 2023 PYQ — Question 73

The mean proportional between (3 + ${\sqrt{5}}$ ) and (15 - ${\sqrt{125}}$ ) is _______.

Show answer & explanation

Correct answer: D

Explanation

The correct answer is option 4 i.e. $2{\sqrt{5}}$ .

Mean proportion $=\sqrt{(3+\sqrt5)(15-\sqrt{125})}$

$=\sqrt{5(3+\sqrt5)(3-\sqrt{5})}$

$=\sqrt{5(9-5)}$

= √20

= 2√5