Step 1: Identify the number of decimal places

The decimal 2.8405 has 4 decimal places.

Step 2: Multiply by the appropriate power of 10

Multiply by 10⁴ = 10000 to eliminate the decimal point.

2.8405 × 10000 = 28405

Step 3: Write as a fraction

Step 4: Simplify the fraction

Find the greatest common divisor (GCD) of 28405 and 10000.

GCD(28405, 10000) = 5

Divide both the numerator and denominator by the GCD: