16 ? 0.4

Dear Student,
1st Assumption is that it is $\frac{16}{0.4}=\frac{160}{4}=40(Multiplying numerator and Denominator by 10)$
2nd Assumption is that it is $16\times 0.4 = 16\times \frac{4}{10}=\frac{64}{10}=6.4$
Regards.