Answer:
0.09923
Step-by-step explanation:
We will first use combination which gives total number of ways of selecting r objects out of n
for :
20C14 =38760 (using calculator)
so assuming sequence of 20 terms, there are 38760 ways of picking the 20 terms.
Each toss there are 2 possible outcomes, total possible outcomes for 20 tosses combined are:
Total possible outcome = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x2 x 2 x 2 x 2 x 2 = =1048576
As given, the girl predicts 14 tosses correctly. so, the probability of getting 14 tosses correct is : P(14 Right)= = = 0.03696
and So on :
P (15 Right) = ==0.01478
P (16 Right) = ==0.0462
P (17 Right) = ==0.001087
P (18 Right) = ==0.000181
P (19 Right) = ==0.000019
P (20 Right) = ==0.000000953
We add all probabilities to get:
Probability of getting 14 or more correct is : P (14 or more) = P(14 Right) + P (15 Right) + ..... + P(20 right) = 0.03696 + 0.01478+0.0462+0.001087+0.000181+0.000019+0.000000953 = 0.09923