Question

小红做练习题用两小时,如果做题速度提高百分之20,那么时间缩短百分之几?

Answer 1

{2 - 1/ [1/2 * (1+20%)] } / 2 = {2 - 1 / [1/2 * 6/5]｝/ 2 = {2 - 1/[3/5]} / 2 = {2 - 5/3} / 2 = {1/3} / 2 = 1/6 = 16.67%