阿荣在实验室用天平称药品时发现令人惊奇的结果:第一次,他把全部药品放在左边盘中,在右边盘中加砝码,称得一个质量w1;然后他又把全部药品放在右盘中,在左盘里加砝码,称得另一个质量w2,发现w1≠w2,这说明天平不准确.他只好取两次重量的算术平均数21(w1+w2)做为药品的质量.(见图 Arong discovered amazing results when he called a drug using a balance in the laboratory. For the first time, he placed all the drugs on the left side plate and added weights to the right side plate. He called a mass w1; then he took it all. The medicine was placed in the right hand plate and a weight was added to the left plate. We called another mass w2 and found w1≠w2. This indicates that the balance was inaccurate. He had to take the arithmetic average of two weights 21 (w1+w2) as The quality of medicines. (See