We read the task carefully. It indicates that Varya is a gambling person and is periodically bought ‘at the probability of a ghost. I really want to get into the prize in every tenth bank. From here you can calculate that the probability of becoming richer –

10: 100 = 0.1 %.

Based on the fact that the sum of happy and unfortunate outcomes is 1, then we get from here

1-0.1 = 0.9.

In the end, we write down only the figure, when it comes to filling out the test form.

Answer: 0.9

1 – the probability of winning if there would be a prize in each bank of coffee.

Under the terms of the task, it is known that in every tenth pack of coffee there is a prize.

Therefore, the probability of getting a prize is 1/10 = 0.1.

In the remaining 9 cases, Varya will lose.

It turns out that the probability of losing varies is 1-0.1 = 0.9.

Only 10 cans. Since the prize is in every tenth, the probability of win 1/10 = 0.1

Always all outcomes in total give 1. We have two outcomes: either won or not.

Then 1 – 0.1 = 0.9 – the probability that Varya will not find a prize in her bank.

Answer: 0.9