Given,

6894.986 + 5025.005 + 600.020 =?

It can be approximated as

6894.986 + 5025.005 + 600.020 =?

$$\begin{gathered} \begin{array}{l}\text{6894.986 + 5025.005 +. 600.020}\\ \downarrow \downarrow \downarrow \\ \text{ 7000 + 5000 + 600}\end{array} \\ = 12600-12520 \end{gathered}$$

Hence, Option E is correct.