Para.18 People are changing careers on average every ten years now,instead of staying in a job for life. on(an/the)average:usually,typically“按平均值， 通常” e.g. On the average,your car was moving at a speed of 25 miles per hour. 你的车速平均为每小时25英里。People are changing careers on average every ten years now, instead of staying in a job for life. on (an/the) average: usually, typically “按平均值， 通常” e.g. On the average, your car was moving at a speed of 25 miles per hour. 你的车速平均为每小时25英里。 Para. 18