A quiz consists of 10 multiple-choice questions, each with 4 possible answers. For someone who makes random guesses for all of the answers, find the...

Borys Shumyatskiy

Hello!

The minimum passing grade is `70%` means at least `7`
questions must be answered correctly. At least `7` means exactly `7` or exactly `8` or exactly
`9` or exactly `10.` All these possibilities are mutually incompatible, so we'll sum up their
probabilities.

The probability of answering each questions correctly is
`1/4,` incorrectly is `3/4.` Denote the number of...

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