The ratio of distance covered in successive seconds for an object under gravity is 1:3:5:7:9... Let the distance in the 1st second be x. The distance in the 5th second is 9x. So, 9x = 27m, which means x=3m. Total height H = x+3x+5x+7x+9x = 25x = 25*3 = 75m.