Multiple choice

In a bag there are $21$ balls marked by number$ 1, 2, 3, .... 21$. Two balls are drawn one by one with replacement. What is the probability that from drawn balls first shows odd number and second shows even number.

  1. $\displaystyle \frac{55}{441}$
  2. $\displaystyle \frac{110}{441}$
  3. $\displaystyle \frac{10}{441}$
  4. $\displaystyle \frac{121}{441}$
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B Correct answer
AI explanation

The total number of balls is 21, consisting of 11 odd-numbered balls and 10 even-numbered balls. Since the draws are with replacement, the probability of drawing an odd number first is 11/21, and the probability of drawing an even number second is 10/21. Using the product rule for independent events, the combined probability is (11/21) * (10/21). The probability is 110/441.

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