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NTA Abhyas JEE Main2020MathematicsProbabilityPractice

Throwing a biased die, a person will get 5 Rupees if he throws the number 5 and will get 8 Rupees for any other number, then the expected income (in Rupees) per throw is (it is given that the number 5 will appear 5 times as frequently as any other number)

Options

  1. A6.5
  2. B7
  3. C5
  4. D5.5

Correct answer

A. 6.5

Step-by-step solution

Let the probability of getting any number other than 5 is P , then the probability of getting 5 is 5 P . ∵ P + P + P + P + P + 5 P = 1 ⇒ P = 1 10 Expected income per throw = 5 10 × 5 + 1 10 × 8 5 = 65 10 = 6.5

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