Question

У продавца 5 зелёных и 4 полосатых арбуза.Сколько арбузов надо купить,чтобы среди них был хотя бы один зелёный?

Answer 1

Нужно купить хотя-бы 5 арбузов

Answer 2

Нужно купить 5 арбузов

Answer 3

Calculating the Number of Watermelons to Buy

To calculate the number of watermelons needed to ensure at least one green watermelon is among them, we can use the concept of complementary events. The probability of not getting a green watermelon in a single purchase is the ratio of the number of non-green watermelons to the total number of watermelons. Therefore, the probability of getting at least one green watermelon in a single purchase is 1 minus the probability of not getting a green watermelon.

Let's calculate the probability and use it to determine the number of watermelons needed.

Calculation

The probability of not getting a green watermelon in a single purchase can be calculated as: P(not green) = (Number of non-green watermelons) / (Total number of watermelons)

Given: - Number of green watermelons = 5 - Number of non-green watermelons = 4

We can calculate the probability of not getting a green watermelon: P(not green) = 4 / (5 + 4) = 4 / 9

The probability of getting at least one green watermelon in a single purchase is: P(at least one green) = 1 - P(not green) = 1 - 4 / 9 = 5 / 9

To ensure a high probability of getting at least one green watermelon, we can calculate the number of watermelons needed using the concept of complementary events: Number of watermelons needed = 1 / P(at least one green)

Let's calculate the number of watermelons needed: Number of watermelons needed = 1 / (5 / 9) = 9 / 5 = 1.8

Since we can't buy a fraction of a watermelon, we would need to round up to the nearest whole number. Therefore, at least 2 watermelons need to be bought to ensure that there is at least one green watermelon among them.

Conclusion

To ensure that there is at least one green watermelon among the purchased watermelons, it is necessary to buy at least 2 watermelons.