A projectile is fired from horizontal ground with speed \( v \) and projection angle \( \theta \). When the acceleration due to gravity is \( g \), the range of the projectile is \( d \). If at the highest point in its trajectory, the projectile enters a different region where the effective acceleration due to gravity is \( g' = \dfrac{g}{0.81} \) then the new range is \( d' = n d \). The value of \( n \) is ________.
