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In basketball, players often have to take free throws - Leaving Cert Mathematics - Question 8 - 2015

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In basketball, players often have to take free throws. When Michael takes his first free throw in any game, the probability that he is successful is 0.7. For all sub... show full transcript

Worked Solution & Example Answer:In basketball, players often have to take free throws - Leaving Cert Mathematics - Question 8 - 2015

Step 1

Find the probability that Michael is successful (S) with all three of his first three free throws in a game.

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Answer

To find the probability that Michael is successful in all three free throws, we calculate:

P(S,S,S)=0.7imes0.8imes0.8=0.448P(S, S, S) = 0.7 imes 0.8 imes 0.8 = 0.448

Step 2

Find the probability that Michael is unsuccessful (U) with his first two free throws and successful with the third.

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Answer

The probability that Michael is unsuccessful in his first two free throws and successful in the third can be calculated as:

P(U,U,S)=0.3imes0.4imes0.6=0.072P(U, U, S) = 0.3 imes 0.4 imes 0.6 = 0.072

Step 3

List all the ways that Michael could be successful with his third free throw in a game and hence find the probability that Michael is successful with his third free throw.

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Answer

The ways for Michael to be successful on his third throw:

  1. Successful on first two throws: S, S, S
  2. Successful on first, unsuccessful on second: S, U, S
  3. Unsuccessful on first two, but successful on third: U, U, S

Calculating the probabilities for each path:

  1. P(S, S, S) = 0.448
  2. P(S, U, S) = 0.7 * 0.2 * 0.6 = 0.084
  3. P(U, U, S) = 0.3 * 0.4 * 0.6 = 0.072

So, the total probability that he is successful on his third free throw:

P=0.448+0.072+0.084=0.604P = 0.448 + 0.072 + 0.084 = 0.604

Step 4

Show that p_{n+1} = 0.6 + 0.2p_n.

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Answer

From the provided definitions, we can align as follows:

pn+1=P(S,S)+P(U,S)=pnimes0.8+(1pn)imes0.6p_{n+1} = P(S, S) + P(U, S) = p_n imes 0.8 + (1 - p_n) imes 0.6 When simplified: =pnimes0.8+0.60.6imespn=0.6+0.2pn= p_n imes 0.8 + 0.6 - 0.6 imes p_n = 0.6 + 0.2p_n

Step 5

Using the result from part (d) (i) above, or otherwise, show that p = 0.75.

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Answer

Assuming for large n, that pn+1ightarrowpp_{n+1} ightarrow p and pnightarrowpp_n ightarrow p, we can equate:

p=0.6+0.2pp = 0.6 + 0.2p Solving yields:

ightarrow 0.8p = 0.6 ightarrow p = 0.75 $$

Step 6

Use the ratio a_{n+1} / a_n to show that a_n is a geometric sequence with common ratio 1/5.

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Answer

Given that an=ppna_n = p - p_n and pnp_n = p thus:

rac{a_{n+1}}{a_n} = rac{p - p_{n+1}}{p - p_n} = rac{0.75 - (0.6 + 0.2p_n)}{0.75 - p_n} = rac{0.15 - 0.2p_n}{0.75 - p_n} By substitution, as nn grows, this ratio approaches 1/51/5. Thus confirmed the geometric sequence.

Step 7

Find the smallest value of n for which p - p_n < 0.00001.

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Answer

Converting the sequence: a1=pp1=0.750.75=0.05a_1 = p - p_1 = 0.75 - 0.75 = 0.05 Then apply for limit convergence: 0.05(1/5)n1<0.000010.05(1/5)^{n-1} < 0.00001 Taking logarithms: (n1)ln(1/5)<ln(0.00001)ln(0.05)(n-1) ln(1/5) < ln(0.00001) - ln(0.05) Results:

ightarrow n = 7 $$

Step 8

Based on this knowledge, what is your estimate of the probability that Michael will be successful with his next free throw in the game?

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Answer

Given his previous success rate, the best estimate of success would be:

  • 0.75 or p

Step 9

Why would it not be appropriate to consider Michael's subsequent free throws in the game as a sequence of Bernoulli trials?

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Answer

This is because events are not independent; the outcome of one throw influences the probability of success in the subsequent throws.

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