A TV tower has a height of 80m. What should be its height if it is to triple its coverage? What is meant by coverage in this questionRANGEor AREACOVERED??

Here we are assuming coverage means maximum area covered(Range). 

Maximum distance covered is given by(d): $\sqrt{2hR}$
Maximum area covered = $\pi$d² = 2$\pi$Rh
where h is the height of the tower and R is radius of the earth.
 
Let A₁ is the maximum area covered when height of the tower is h₁= 80 m
A_​2 is the maximum area covered when height of the tower is h₂ 

A₂ = 3A₁
$2\pi R$h₂ = 3×$2\pi R$h₁
h₂ = 3h₁
 =  3×80
 = 240 m

Required height of the tower is 240 m.