Question

一杯纯牛奶,先喝掉20%,然后加满水搅拌,接着喝去半杯,杯子中所剩的纯牛奶是原有纯牛奶的百分之几?

Answer 1

1-20%=80%

80%×50%=40%

1-（20%+40%）=40%

40%÷1=40%

答：还剩原有的40%.