If the height of the TV tower is increased by 21%, then by what percentage will the transmission range of the tower be affected?

10%

The correct answer is Option (3) → 10%

The transmission range of a TV tower is,

$R∝\sqrt{h}$   [h = height of tower]

if the height of the tower is increased by 21%,

$h'=1.21h$

$∴R'\sqrt{h'}=\sqrt{1.21h}=1.1\sqrt{h}$

The transmission range of the tower will increased by 10%.