英语翻译关於倍数的翻译:Output in this company is now six times ---- it

这里what=of that=of which,所以只要不限制字数,what和of that(或者of which)都可以填.
因为that或which引导定语从句,必须要有其修饰的对象,显然这里没有,所以不能直接用that或which.而用what则是宾语从句,直接这样用是可以的,相当于：Output in this company is now five times higher than what it was before 1990.
加of则形成介宾短语,相当于这样的句子:Red one is three times of blue one.=Red one is 2 times longer than blue one.