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STEP I 1997 question 13 solution
From The Student RoomTSR Wiki > Study Help > Subjects and Revision > Mathematics > STEP > STEP 1997 Solutions > STEP I 1997 question 13 solution Probability for Mr's to plant the traps: Mr1 = 1/10, Mr2 = 2/10, Mr3 = 3/10, Mr4 = 4/10 The probabilities for the vicious attack canary can be disregarded as we get to know that Mr Blond hear it isn't such a thing in the room... Probability for anaconda being at present: Mr1 = 2/7, Mr2 = 3/7, Mr3 = 4/7, Mr4 = 5/7 Probability for bomb being at present: Mr1 = 1/7, Mr2 = 2/7, Mr3 = 3/7, Mr4 = 4/7
Total probability of there being a bomb Probability for placements of anacondas: Mr1 = (1/10)(2/7), Mr2 = (2/10)(3/7), Mr3 = (3/10)(4/7), Mr4 = (4/10)(5/7) Total probability of there being an anaconda Now Mr Blond has two choices, turn on the light or let it be turned off... Probability of ending up dead by chosing: Turning it on: (4/7)(1/3) by anaconda, (3/7)(1/2) by bomb, Total: Leaving it turned off: (4/7)(1/2) by anaconda, (3/7)0 by bomb, Total: This means that the probability of dying is higher if Mr Blond turns the light on, hence he should leave it off.
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