Last three digits

Since in the expansion of 2^{-n} there are always some zeroes which ends with some 5^{n} like in 2^{-2} decimal expansion is .25 and in 2^{-3} there are 3 digits .125 and so on.... So in the expansion of 2^{-45}. We can write its unit digits as (5^{3})^{15} and we know that in 5^3 the digits are 125

For any integer $n\geq0$ , the decimal expansion of $2^{-n}$ always starts with a certain number of zeroes and ends with $5^n$ . We also know that for any odd integer $n\geq3$ , the last three digits of $5^n$ is $\boxed{125}$ .