[填空题]
In a college lottery, there are tp-j;pvz8 3yb j)4kh8vd6 zhyrwo types 5x3paem 3f5yrof tickets: 'standard' tickets and 'lucky' tickets. Every student is given one ticket at random. The total number of the standard tickets is four times greater than the numberp 53ym3 exr5af 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. ≈
