Concept:
The weight of yarn in the "tex" system is defined as the mass in grams per 1000 metres of yarn.
Step 1: Applying the Tex Formula.
The weight of a single yarn can be calculated as:
$$Weight (g) = \frac{Tex \times Length (m)}{1000}$$
Step 2: Calculating for Multiple Ends.
Since there are 2000 ends, the total length is $2000 \times 1000$ metres.
$$Total Weight (g) = \frac{20 \text{ tex} \times (2000 \text{ ends} \times 1000 \text{ m})}{1000}$$
$$Total Weight (g) = 20 \times 2000 = 40,000 \text{ g}$$
Step 3: Converting to Kilograms.
$$Weight (kg) = \frac{40,000}{1000} = 40 \text{ kg}$$