Below is an instruction that describes a task. Write a response that appropriately completes the request in Chinese. Please answer in Chinese.

### Instruction:
 一个矩形的长度是宽度的四倍。如果面积是100平方米，矩形的长度是多少？


### Response:
 假设矩形的宽度为x。
矩形的长度为4x。
矩形的面积为x * 4x = 100平方米。
4x * x = 100
3x * x = 100
x * x = 30
x = <<5=5>>5
矩形的长度为4 * 5 = <<4*5=20>>20米。