[填空题]
In a college lottery, tswi.r noi5r. 9here are i86 m havdpggyeu 98h-/.6 u5eud wx)rtwo types of tickets: 'standard' tickets and 'lucky' tickets. Every student is g 9uyi6 ameveh)d8gxpu u r8wgd6.h -5/iven one ticket at random. The total number of the standard tickets is four times greater than the number of lucky tickets.
The probability of winning the lottery with a standard ticket is $ \frac{1}{100} and \frac{1}{40}$ for a lucky ticket. The tree diagram below illustrates this.
1. Calculate the probability that a randomly chosen student will win the lottery.
2. Calculate the probability that a randomly chosen student will get a lucky ticket and still lose the lottery.
3. Calculate the probability that a randomly chosen student, given they won the lottery, had a standard ticket. ≈
