有人问到这样一道改错题：

(1)You read different things with different speed.

有人说different speed不可数，故而不错，对吗？

不对。speed在此是一可数名词，故而上述句（1）应改作：

(2)You read different things with different speeds.

复数形式speeds并不罕见，再如：

(3)My bicycle has ten speeds .

(4)This car is capable of reaching speeds of over 110 kilometres per hour.