The score when two fair six-sided dice are thrown is the sum of the two numbers on the upper faces. The two dice are thrown repeatedly until a score of 4 is obtained. The number of throws taken is denoted by the random variable $$$X$$$. Find the mean of $$$X$$$. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

Mathematics

IGCSE&ALevel

CAIE

Exam No：9709_s20_qp_51 Year：2020 Question No：1(b)

Answer:

Mean $=\frac{1}{\frac{1}{12}}=12$

Knowledge points:

5.4.3 use formulae for the expectation and variance of the binomial distribution and for the expectation of the geometric distribution. (Proofs of formulae are not required.)

Answer:

Knowledge points:

Solution:

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