如果列中的值大于某个值，则从数组中删除行

I have the following code:

我有以下代码:

import numpy as np
a=np.array([[1.1,5,100],[2.4,6,200],[3.3,7,300],[4.1,8,400],[4.9,9,500],[5.5,10,600],[6,5],700,[6.5,12,800],[7.2,20,900],[8,20,1000]])
b=np.max(a[:,0])#finds maximum value in 1st column(index=0)
if b > 5:
   Do something
import n