To solve this problem, we use the combination equation to
find for the possible groups of answer to the questions. Since we are looking
for at least 5 correct answers out of 10 questions, therefore we find for 10
≥
r ≥ 5. We use the formula for combination:
nCr = n! / r! (n – r)!
Where,
n = total number of questions = 10
r = questions with correct answers
For 10 ≥ r ≥ 5:
10C5 = 10! / 5! (10 – 5)! = 252
10C6 = 10! / 6! (10 – 6)! = 210
10C7 = 10! / 7! (10 – 7)! = 120
10C8 = 10! / 8! (10 – 8)! = 45
10C9 = 10! / 9! (10 – 9)! = 10
10C10 = 10! / 10! (10 – 10)! = 1
Summing up all combinations will give the total
possibilities:
Total possibilities = 252 + 210 + 120 + 45 + 10 + 1 = 638
Answer: 638
