Brain Teasers & Mental Math
Roll a single die. If it lands on 6, you roll again and add; you keep rolling and adding as long as you roll a 6. What is the expected total?
Model answer
Let E be the expected total. E = (1/6)(1+2+3+4+5) + (1/6)(6 + E) = 15/6 + 1 + E/6. So E − E/6 = 15/6…
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