Question

There are 15 questions on a 4 option multiple choice test. George guesses at the answers.

Find: P(7 correct)
Find: P(getting at most 30%)

Answer 1

P(7 correct) is approximately 8%

P(≤ 30%) would be 4 out of 15 questions or 26.7%

Explanation:

P(7 correct) would be 1/4 multiplied 15 times (one option for each question)

1/4 x 15 = 7/60 ≈ 8.1%

If you do guess-and-check and begin with assuming 3 correct answers then 3 out of 15 is 20%

Now we can try 4 correct answers and 4 out of 15 is 26.7%

If we try 5 out of 15 that is the same as 1/3 which is 33.3%

Since we can half a fractional portion of an answer correct then the correct number would be 4 correct out of 15 (which gives us 26.7%)