What is 99.9.9.9.9 times 8.888.8.88?

Ebbinghaus forgetting curve shows that forgetting is not in the same proportion with the passage of time. When the learning content is just memorized, it is recalled every 20 minutes, and the forgetting rate is 42%; after one hour of re examination, the retention rate is about 44%, and the forgetting rate is 56%; after one day of re examination, the retention rate is 33%, and the forgetting rate is 67%; after six days of re examination, the retention rate is 33%, and the forgetting rate is 67%, The retention rate is 25%; one month later, the retention rate is 21.9%. Since then, forgetting is basically no longer forgotten. It can be seen that forgetting exists objectively, and its rule is fast first and then slow, more first and then less. According to this rule, the knowledge just learned should be reviewed and consolidated in time, with more times at the beginning of review and shorter interval time, and then reduce the number of reviews and expand the interval, Grasping the law and consolidating it in time are the powerful guarantee of memory

1/2+1/6+1/12+...+1/56=
fast

1/2+1/6+1/12+...+1/56
=1/2+1/(2*3)+1/(3*4)+…… +1/(7*8)
=1/2+(3-2)/(2*3)+…… +(8-7)/(8*7)
=1/2+1/2-1/3+1/3-1/4+…… +1/7-1/8
=1-1/8
=7/8

There are 60 students in a class. One fifth of the boys are more than one fourth of the girls. How many boys and girls are there in this class?

Number of male students (3 + 1 / 4x60) / (1 / 5 + 1 / 4) = 40
Number of female students 60-40 = 20

There are 50 students in class one of grade six. After 25 male students are selected to participate in the speech contest, the number of female students is 57% of that of the remaining male students?

A: there are 35 boys and 15 girls in class 1 of grade 6

What is 99.9.9.9.9 times 8.888.8.88?