Chapter 15: Q6MP (page 776)
Find the number of ways of putting 2 particles in 5 boxes according to the different kinds of statistics.
Short Answer
The solution is derived as mentioned below.
Chapter 15: Q6MP (page 776)
Find the number of ways of putting 2 particles in 5 boxes according to the different kinds of statistics.
The solution is derived as mentioned below.
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Get started for free(a) Set up a sample space for the 5 black and 10 white balls in a box discussed above assuming the first ball is not replaced. Suggestions: Number the balls, say 1 to 5 for black and 6 to 15 for white. Then the sample points form an array something like (2.4), but the point 3,3 for example is not allowed. (Why?
What other points are not allowed?) You might find it helpful to write the
numbers for black balls and the numbers for white balls in different colors.
(b) Let A be the event โfirst ball is whiteโ and B be the event โsecond ball is
black.โ Circle the region of your sample space containing points favorable to
A and mark this region A. Similarly, circle and mark region B. Count the
number of sample points in A and in B; these are and . The region
AB is the region inside both A and B; the number of points in this region is
. Use the numbers you have found to verify (3.2) and (3.1). Also find
and and verify (3.3) numerically.
(c) Use Figure 3.1 and the ideas of part (b) to prove (3.3) in general.
Some transistors of two different kinds (call them N and P) are stored in two boxes. You know that there are 6 Nโs in one box and that 2 Nโs and 3 Pโs got mixed in the other box, but you donโt know which box is which. You select a box and a transistorfrom it at random and find that it is an N; what is the probability that it came from the box with the 6 Nโs? From the other box? If another transistor is picked from the same box as the first, what is the probability that it is also an N?
(a) Three typed letters and their envelopes are piled on a desk. If someone puts theletters into the envelopes at random (one letter in each), what is theprobabilitythat each letter gets into its own envelope? Call the envelopes A, B, C, and thecorresponding letters a, b, c, and set up the sample space. Note that โa in A,b in B, c in Aโ is one point in the sample space.
(b) What is the probability that at least one letter gets into its own envelope?
Hint: What is the probability that no letter gets into its own envelope?
(c) Let A mean that a got into envelope A, and so on. Find the probability P(A)that a got into A. Find P(B) and P(C). Find the probability P(A + B)that either a or b or both got into their correct envelopes, and the probabilityP(AB) that both got into their correct envelopes. Verify equation (3.6).
Two decks of cards are โmatched,โ that is, the order of the cards in the decks is compared by turning the cards over one by one from the two decks simultaneously; a โmatchโ means that the two cards are identical. Show that the probability of at least one match is nearly.
Given a family of two children (assume boys and girls equally likely, that is, probability for each), what is the probability 1/2 that both are boys? That at least one is a girl? Given that at least one is a girl, what is the probability that both are girls? Given that the first two are girls, what is the probability that an expected third child will be a boy?
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