The value of 20 kg of old Lego Duplo and Lego Duplo trains can vary depending on the condition, rarity, and demand for the specific pieces. Generally, old Lego Duplo sets and trains can be worth anywhere from $5 to $20 per kilogram, so 20 kg could be worth between $100 to $400. However, if there are rare or sought-after pieces in the collection, the value could be higher. It's best to research current market prices and consider factors such as condition and completeness of the sets to determine a more accurate value. **

To combine Lego Duplo pieces, you can simply stack them on top of each other or attach them side by side using the studs and holes on the bricks. You can also use specialty pieces like connectors, bridges, and hinges to create more complex structures. The key is to experiment and be creative with how you connect the pieces to build unique and imaginative creations. **

As an AI, I do not have the ability to buy or sell physical products. My main purpose is to provide information and assistance to users. If you are looking to sell Duplo Lego, you may want to consider online marketplaces, local toy stores, or second-hand shops as potential options. **

As an AI, I do not have personal preferences. However, if you are considering selling Duplo Lego, it could be a good idea as there is a demand for it among parents with young children. Duplo Lego is known for its durability and educational benefits, making it a popular choice for families looking to engage their children in creative play. Additionally, selling Duplo Lego could also help you declutter and make some extra money in the process. **

To clean LEGO Duplo bricks, you can start by separating the bricks by color and size. Then, you can wash them in warm soapy water using a mild detergent and a soft-bristled brush to gently scrub away any dirt or grime. After washing, rinse the bricks thoroughly with clean water and allow them to air dry completely before storing them. Avoid using harsh chemicals or abrasive materials that could damage the bricks. **

The Lego brick doesn't come off easily because of the design of the interlocking studs and tubes. When two Lego bricks are pressed together, the studs on one brick fit snugly into the tubes on the other brick, creating a strong connection. This design allows the bricks to stay firmly attached while still being easy to separate when intentionally pulled apart. Additionally, the material used to make Lego bricks, ABS plastic, provides just the right amount of flexibility and durability to maintain a secure connection. **

The cost of a Lego brick can vary depending on the size, color, and specific set it comes from. On average, a single Lego brick can cost anywhere from 10 to 20 cents. However, specialty or rare bricks can be more expensive, while larger sets may offer a lower cost per brick. Ultimately, the price of a Lego brick depends on a variety of factors. **

The price you can ask for Lego Duplo sets can vary depending on factors such as the specific set, its condition, and the current market demand. Generally, you can research the prices of similar sets on online marketplaces such as eBay or Amazon to get an idea of the range. Additionally, consider the original retail price, the rarity of the set, and any additional accessories or pieces included when determining the asking price. It's also helpful to take into account the condition of the set and whether it is new, used, or complete. **