Li Ping is a Grade Eight student in Nanjing Sunshine Secondary School. The table below is his mid-term self-assessment(自我评价).He draws faces to show his progress:
实验室现有98%的浓硫酸,但实验中经常要用到较稀的硫酸。现要把50g质量分数98%的浓硫酸稀释成20%的稀硫酸,需加入多少克水?
____°
____角
— Can Jane and Jill swim?
— No, they .