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Answer:
The probability is 0.9211
Step-by-step explanation:
Let's call K the event that the student know the answer, G the event that the student guess the answer and C the event that the answer is correct.
So, the probability P(K/C) that a student knows the answer to a question, given that she answered it correctly is:
P(K/C)=P(K∩C)/P(C)
Where P(C) = P(K∩C) + P(G∩C)
Then, the probability P(K∩C) that the student know the answer and it is correct is:
P(K∩C) = 0.7
On the other hand, the probability P(G∩C) that the student guess the answer and it is correct is:
P(G∩C) = 0.3*0.2 = 0.06
Because, 0.3 is the probability that the student guess the answer and 0.2 is the probability that the answer is correct given that the student guess the answer.
Therefore, The probability P(C) that the answer is correct is:
P(C) = 0.7 + 0.06 = 0.76
Finally, P(K/C) is:
P(K/C) = 0.7/0.76 = 0.9211
Answer:
520,000
Step-by-step explanation:
1400 x 200 = 280000
(400 + 800) x 400 /2 = 240000
240000 + 280000 = 520000
26-72 million because It has to be greater than 25 and less than 73 so you you a number in between
