Step 1: Identify the number of decimal places

The decimal 13.990428 has 6 decimal places.

Step 2: Multiply by the appropriate power of 10

Multiply by 10⁶ = 1000000 to eliminate the decimal point.

13.990428 × 1000000 = 13990428

Step 3: Write as a fraction

Step 4: Simplify the fraction

Find the greatest common divisor (GCD) of 13990428 and 1000000.

GCD(13990428, 1000000) = 4

Divide both the numerator and denominator by the GCD: