Sturdy Numarkasten! Perfect for Montessori and STEAM learning to eliminate stumbling blocks in arithmetic! ■ The Difficulty of Subtraction with Borrowing For example, when subtracting with borrowing, such as "12 - 7", how do you teach children? Generally, you calculate "10 - 7" and add the answer "3" to the "2" in 12. However, there's a challenge with this. It involves two subtractions and one addition in a single calculation. ■ What is a Ten Key? This is where the ten key comes in handy. A ten key is a number that, when added to a given number, equals 10. The ten key for 7 is 3, and the ten key for 6 is 4. Children who are good at math actually grasp this as an "image." In other words, they instantly know that the ten key for 4 is 6, and the ten key for 2 is 8. You might think it's just doing 10 - 6 or 10 - 2, but it's different. The key is "visualizing it so you can understand it instantly." Then, even in the calculation of 12 - 7, you can instantly see that you should "calculate 2 + 3." The calculation is done only once. ■ Train Ten Keys Visually with Numarkas What's important is visualizing numbers and getting off to a quick start. Math is a subject that builds upon itself. If you stumble at the beginning, it's difficult to catch up. Conversely, if you can instantly determine the ten key through visualization and solve problems faster than other children, it leads to confidence and further improvement in grades. Subtraction with borrowing is the first hurdle. I strongly recommend visualizing the ten keys. ■ Features of This Product ・Sturdy resin case ・The golden ratio is engraved on the back of the box ・The size of the box itself is also the golden ratio. Mathematical beauty at your fingertips! ・Slide-type lid that clicks into place ・By sliding the lid halfway, you can hide how many marbles are on one side ・You can roll the marbles with the lid closed ■ Contents ・Numarkas body [Brown] ・Marbles [10 marbles] Color (Please comment your preference from blue, light blue, white, and yellow) + Add 10 more marbles for 200 yen. Please comment your choice before purchasing. Size (approx.) Width 15, Length 10, Height 3cm Numarkas Early childhood education Educational toys Nature Science Please refrain from purchasing if you are concerned about the details, as this is a sale by an amateur. Discounts are available for multiple purchases and repeat customers, so please comment.