When height of the tower is increased by 21 % then transmission range of tower will be affected by x % then what is x

Let  h1=h   and    h2=h+21%of h = 1.21 h   We know that,  d=2Rh ∴ d ∝ h ⇒d2d1=h2h1 ⇒d2d=1.21hh = 1.1 ⇒d2=1.1d   Now, Percentage change = △dd×100%=d2−d1d2×100%                                                                             =1.1d−dd×100%=10%