Step 1: Identify the number of decimal places

The decimal 0.644 has 3 decimal places.

Step 2: Multiply by the appropriate power of 10

Multiply by 10³ = 1000 to eliminate the decimal point.

0.644 × 1000 = 644

Step 3: Write as a fraction

Step 4: Simplify the fraction

Find the greatest common divisor (GCD) of 644 and 1000.

GCD(644, 1000) = 4

Divide both the numerator and denominator by the GCD: