小兰P263.89

A recent national study of the public schools shows that there are now one microcomputer for every thirty-two puplis,four times as many than there were four years ago.

答案是 there is now one microcomputer for every thirty-two pupils,four times as many as there were.

NN们帮忙解释下为什么最后是there were呢，按照平对称原则也应该是there was啊~~