In an objective paper, there are two sections of 10 questions each. For "section 1" , ech question has 5 options and only one option is correct and "sectin 2" has 4 option with multiple answer an marks for a question in this section is awarded only if he ticks all correct answers. Marks for each question in "section 1" is 1 and in "section 2" is 3. (therefore is no negativve marking.)
If a candidate attempts only two questions by guessing, one from "section 1" and one from "section 2", the probability that he score in both questions is

Options

A. `(1//75)^(10)`
B. `1-(1//75)^(10)`
C. `(74//75)^(10)`
D. None of these

Answer

B

Explanation

To get 40 marks, he has to answer all questions correctly and its probability is `(1//5)^(10)(1//15)^(10).` Hence, probability of getting a score less than 40 is
`1-((1)/(5))^(10)((1)/(15))^(10)=1-((1)/(75))^(10)`