加减法演示机械装置（附安装步骤）/Addition and subtraction demonstration mechanical device(Installation steps)
注：额外配件：直径4高度3圆磁铁x50（相互接触磁铁，磁极相反安装）
家里小孩子开始学加减法了，一直和他讲不清楚。干脆做一个演示的机械结构
使用方法：摇柄向内摇一圈是加，往外摇一圈是减，第一个数字是要计算的数字，第二个数字是结果的十位，第三个数字是结果的个位，
例如计算8+7-3，先把第一个数字转到8，向内摇一圈，在把第一个数字调到7，向内摇一圈，再把第一个数字转到3，向外摇一圈，后面两个数字就会显示算式结果12.
Note: Additional accessories: diameter 4, height 3, round magnet x50 (magnets in contact with each other, installed with opposite magnetic poles)
My child at home has started learning addition and subtraction, but I still can't explain it clearly to him. Why not create a mechanical structure for demonstration
Usage: Turn the crank inward for addition and outward for subtraction. The first number is the digit to be calculated, the second is the tens place of the result, and the third is the ones place of the result,
For example, to calculate 8+7-3, first turn the first number to 8 and rotate it inward once, then adjust the first number to 7 and rotate it inward again, followed by turning the first number to 3 and rotating it outward once. The last two numbers will then display the result of the calculation, which is 12
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