Notice that in the number 0.4, the decimal point appears shifted one place to the right with respect to the number 0.04. When we multiply a number by the power 10^n, the decimal point is shifted n places to the right. Therefore, the power of 10 needed to move the decimal point from 0.04 one place to the right to get 0.4 is 1.
Therefore, the missing power of the base 10 is:
[tex]1[/tex]So, we can write:
[tex]0.04\times10^1=0.4[/tex]