Let the drops fall at a regular interval of time t.

When the fifth drop starts falling, the time elapsed will be $t,2t,3t$ and $4t$ for the fourth , third, second and first drop respectively and if the distances covered are $S_4,S_3,S_2,S_1$ then

$S_1= \large\frac{1}{2}$$g(4t)^2=16 \times \large\frac{1}{2}$$gt^2$

$S_2= \large\frac{1}{2}$$g(3t)^2=9 \times \large\frac{1}{2}$$gt^2$

$S_3= \large\frac{1}{2}$$g(2t)^2=4 \times \large\frac{1}{2}$$gt^2$

$S_4= \large\frac{1}{2}$$g(t)^2= \large\frac{1}{2}$$gt^2$

Here $S_1= 16 m$ Therefore $\large\frac{1}{2}$$gt^2=1m$

Hence $S_2= 9 m,S_3= 4 m$ and $S_1 =1m$ .

The height of the various drops from the surface of the earth will be $0,7,12,15\;and \;16 m$