Let us assume we have an eight face die numbered from 1 to 8. What is...
Probability of exactly two numbers appearing on the top face in five throws of an eight-faced die
To find the probability of exactly two numbers appearing on the top face in five throws of an eight-faced die, we need to calculate the total number of favorable outcomes and divide it by the total number of possible outcomes.
Total number of possible outcomes:
Since each throw of the die can result in any number from 1 to 8, there are 8 possible outcomes for each throw. As there are a total of 5 throws, the total number of possible outcomes is 8^5 = 32768.
Total number of favorable outcomes:
To calculate the total number of favorable outcomes, we need to consider the different ways in which exactly two numbers can appear on the top face in five throws.
Case 1: Two different numbers appear twice each, and one number appears once.
In this case, we need to choose two numbers out of 8, which can be done in 8C2 ways. Once the two numbers are chosen, we need to arrange them in the five throws, which can be done in 5C2 ways. The remaining number can be chosen in 6 ways. Therefore, the total number of favorable outcomes for this case is 8C2 * 5C2 * 6 = 28 * 10 * 6 = 1680.
Case 2: One number appears three times, and two different numbers appear once each.
In this case, we need to choose one number out of 8, which can be done in 8C1 ways. Once the number is chosen, we need to arrange it in the five throws, which can be done in 5C3 ways. The remaining two numbers can be chosen in 7C2 ways. Therefore, the total number of favorable outcomes for this case is 8C1 * 5C3 * 7C2 = 8 * 10 * 21 = 1680.
Total number of favorable outcomes:
The total number of favorable outcomes is the sum of the favorable outcomes from both cases: 1680 + 1680 = 3360.
Probability:
Finally, we can calculate the probability by dividing the total number of favorable outcomes by the total number of possible outcomes.
Probability = Total number of favorable outcomes / Total number of possible outcomes = 3360 / 32768 = 840 / 8192 = 840 / 32768.
Hence, the correct answer is option A) 840/32768.
Let us assume we have an eight face die numbered from 1 to 8. What is...
Total Number of possible outcomes = 8
5Selecting any two numbers from 1 to 8 = 8C2
These two numbers should appear in all 5 throws. Let us say, x and y are those two numbers. Thus, first throw should result in either x or y. Similarly for all subsequent throws.
But, all throws should not result in the same number.
Required probability=8C2*(25 - 2)/ 85
= 840/32768.
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