Article in English: For example, if the original price of a computer was $200, type “200” in cell A1. For example, if you ultimately paid $150 for the computer, type “150” in cell B1. When you do this, Excel automatically calculates the difference between the two prices and displays the numerical value in the cell. For this example, the numerical value in cell C1 should be 50 if you enter the formula correctly. When you do this, Excel divides the price difference by the original price. For this example, the numerical value in cell D1 should be 0.25 if you enter the formula correctly. When you do this, Excel converts the decimal into a percentage.  In this example, the value in cell D1 should be 25%. This means that you saved 25 percent on the purchase of the computer. Because you entered formulas into the other cells, Excel will automatically update the cost savings percentage when you change the original price or the final price, or both. For example, say you also purchased a lamp for $10 that originally cost $17. If you type “17” into cell A1 and “10” into B1 -- and leave all the other cells as they are – the corresponding savings of 41 percent will display in cell D1.

Summary in Chinese:
在A1单元格输入产品或服务的原价，按回车键。 在B1单元格输入所有折扣后的最终价，按回车键。 在C1单元格中输入公式“=A1-B1”并按回车。 在D1单元格输入公式“=C1/A1”并按回车。 光标选中D1单元格，按住“CRTL+SHIFT+%”。 在A1和B1输入新值，可以计算其他买卖的成本节约率。