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In an objective paper, there are two sec...

In an objective paper, there are two sections of 10 questions each.For "section 1", each question has 5 options and only one optionis correct and "section 2" has 4 options with multiple answers and marks for a question in this section is awarded only if he ticks all correct answers. Marks for each question in "sectionl 1" is 1 and in "section 2" is 3. (There is no negative marking.) If a candidate attempts only two questions by guessing, one from "section 1" and one from "section 2", the probability that he scores in both question is `74/75`

A

`74//75`

B

`1//25`

C

`1//15`

D

`1//75`

Text Solution

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The correct Answer is:
To solve the problem step by step, we need to calculate the probability of scoring in both sections when a candidate guesses one question from each section. ### Step 1: Calculate the Probability for Section 1 In Section 1, there are 5 options for each question, and only one of them is correct. Therefore, the probability of guessing the correct answer is: \[ P(\text{Correct in Section 1}) = \frac{1}{5} \] ### Step 2: Calculate the Probability for Section 2 In Section 2, there are 4 options, and multiple answers can be correct. We need to find the total number of ways to select the correct answers: 1. **One option correct**: There are 4 ways (choose 1 from 4). 2. **Two options correct**: The combinations are: - (1, 2) - (1, 3) - (1, 4) - (2, 3) - (2, 4) - (3, 4) This gives us a total of 6 ways. 3. **Three options correct**: The combinations are: - (1, 2, 3) - (1, 2, 4) - (1, 3, 4) - (2, 3, 4) This gives us a total of 4 ways. 4. **All options correct**: There is only 1 way (1, 2, 3, 4). Now, we sum these possibilities to find the total number of ways to select the correct answers in Section 2: \[ \text{Total ways} = 4 + 6 + 4 + 1 = 15 \] Thus, the probability of guessing the correct answer in Section 2 is: \[ P(\text{Correct in Section 2}) = \frac{1}{15} \] ### Step 3: Calculate the Combined Probability To find the probability that the candidate scores in both questions (one from each section), we multiply the probabilities from both sections: \[ P(\text{Correct in both sections}) = P(\text{Correct in Section 1}) \times P(\text{Correct in Section 2}) = \frac{1}{5} \times \frac{1}{15} = \frac{1}{75} \] ### Conclusion The final probability that the candidate scores in both questions is: \[ \frac{1}{75} \]

To solve the problem step by step, we need to calculate the probability of scoring in both sections when a candidate guesses one question from each section. ### Step 1: Calculate the Probability for Section 1 In Section 1, there are 5 options for each question, and only one of them is correct. Therefore, the probability of guessing the correct answer is: \[ P(\text{Correct in Section 1}) = \frac{1}{5} \] ...
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