Use a dump truck to subtract unwanted balls through a chute.As the children roll the balls in and out of the truck, they visualise the process of subtraction with the help of physical cues which leads to a concrete understanding of subtraction. They also begin to understand that addition and subtraction are related processes that are opposite of each other in nature. This toy improves dexterity as children learn to operate the dump truck with their hands, opening and shutting the gate to let the balls pass. This kind of constant engagement also keeps them excited about the learning process.
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https://www.youtube.com/watch?v=JT3yHlxeuVw