Express Decimal 1.39: Number Representation Practice

To solve the problem of converting $1.39$ to a mixed number, follow these steps:

• Step 1: Recognize that the number $1.39$ consists of a whole number, $1$, and a decimal, $0.39$.
• Step 2: Convert the decimal $0.39$ into a fraction. Since there are two digits after the decimal point, it is equivalent to $\frac{39}{100}$.
• Step 3: Combine this fraction with the whole number from Step 1 to form the mixed number $1\frac{39}{100}$.

Therefore, the correct answer is $1\frac{39}{100}$.