Step 1: Identify the number of decimal places

The decimal 2.639 has 3 decimal places.

Step 2: Multiply by the appropriate power of 10

Multiply by 10³ = 1000 to eliminate the decimal point.

2.639 × 1000 = 2639

Step 3: Write as a fraction

Step 4: Simplify the fraction

Find the greatest common divisor (GCD) of 2639 and 1000.

GCD(2639, 1000) = 1

Divide both the numerator and denominator by the GCD: