A camera shop stocks eight different types of batteries, one of which is type A76. Assume there are at least 32 batteries of each type. (a) How many ways can a total inventory of 32 batteries be distributed among the eight different types? Following the model of Example 9.6.2, represent each way of distributing the inventory as a string of types of batteries corresponding to the spaces around the vertical bars and the batteries corresponding to the crosses. It follows that the number of ways the total inventory can be distributed is vertical bars and crosses, with the (b) How many ways can a total inventory of 32 batteries be distributed among the eight different types if the inventory must include at least four A76 batteries? (c) How many ways can a total inventory of 32 batteries be distributed among the eight different types if the inventory includes at most three A76 batteries?

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
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A camera shop stocks eight different types of batteries, one of which is type A76. Assume there are at least 32 batteries of each type.
(a) How many ways can a total inventory of 32 batteries be distributed among the eight different types?
Following the model of Example 9.6.2, represent each way of distributing the inventory as a string of
types of batteries corresponding to the spaces around the vertical bars and the batteries corresponding to the crosses. It follows that the number of ways the total
inventory can be distributed is
vertical bars and
crosses, with the
(b) How many ways can a total inventory of 32 batteries be distributed among the eight different types if the inventory must include at least four A76 batteries?
(c) How many ways can a total inventory of 32 batteries be distributed among the eight different types if the inventory includes at most three A76 batteries?
Transcribed Image Text:A camera shop stocks eight different types of batteries, one of which is type A76. Assume there are at least 32 batteries of each type. (a) How many ways can a total inventory of 32 batteries be distributed among the eight different types? Following the model of Example 9.6.2, represent each way of distributing the inventory as a string of types of batteries corresponding to the spaces around the vertical bars and the batteries corresponding to the crosses. It follows that the number of ways the total inventory can be distributed is vertical bars and crosses, with the (b) How many ways can a total inventory of 32 batteries be distributed among the eight different types if the inventory must include at least four A76 batteries? (c) How many ways can a total inventory of 32 batteries be distributed among the eight different types if the inventory includes at most three A76 batteries?
Example 9.6.2
Selecting 15 Cans of Soft Drinks of Five Different Types
A person giving a party wants to set out 15 assorted cans of soft drinks for his guests. He
shops at a store that sells five different types of soft drinks.
a. How many different selections of cans of 15 soft drinks can he make?
b. If root beer is one of the types of soft drink, how many different selections include at
least six cans of root beer?
C. If the store has only five cans of root beer but at least 15 cans of each other type of
soft drink, how many different selections are there?
ors nod
2wank or
Solution
a. Think of the five different types of soft drinks as the n categories and the 15 cans of
soft drinks to be chosen as ther objects (so n = 5 and r = 15). Each selection of cans
of soft drinks is represented by a string of 5-1 = 4 vertical bars (to separate the
categories of soft drinks) and 15 crosses (to represent the cans selected). For instance,
the string
odmun odi oos
x x × | ×
X x x × × ||× × × | × X
represents a selection of three cans of soft drinks of type 1, seven of type 2, none of
) ted Isor type 3, three of type 4, and two of type 5. The total number of selections of 15 cans of
to odo of soft drinks of the five types is the number of strings of 19 symbols, 5-1= 4 of them|
ed
and 15 of them X:
to 1odr
(*)-
6 2
19.18 17 16 15!
15+5-1
19!
(19)
15
151 -4-3-2-1
= 3,876.
15!·(19 – 15)!
15
b. If at least six cans of root beer are to be included in the selection, you can imagine
choosing six such cans first and then choosing nine additional cans. The choice of the
nine additional cans can be represented as a string of 9 ×'s and 4 's. For example, if
root beer is type 1, then the string X × X || X X |X X X X | represents a selection
of three cans of root beer (in addition to the six chosen initially), none of type 2. two
of type 3, four of type 4, and none of type 5. Thus the total number of selections of
15 cans of soft drinks of the five types, including at least six cans of root beer, is the
number of strings of 13 symbols, 4 (=5 – 1) of them | and 9 of them ×:
9+4
13 12-11 10-9!
91 -4-3-2-1
13!
13
9!-(13 – 9)!
9
= 715.
Transcribed Image Text:Example 9.6.2 Selecting 15 Cans of Soft Drinks of Five Different Types A person giving a party wants to set out 15 assorted cans of soft drinks for his guests. He shops at a store that sells five different types of soft drinks. a. How many different selections of cans of 15 soft drinks can he make? b. If root beer is one of the types of soft drink, how many different selections include at least six cans of root beer? C. If the store has only five cans of root beer but at least 15 cans of each other type of soft drink, how many different selections are there? ors nod 2wank or Solution a. Think of the five different types of soft drinks as the n categories and the 15 cans of soft drinks to be chosen as ther objects (so n = 5 and r = 15). Each selection of cans of soft drinks is represented by a string of 5-1 = 4 vertical bars (to separate the categories of soft drinks) and 15 crosses (to represent the cans selected). For instance, the string odmun odi oos x x × | × X x x × × ||× × × | × X represents a selection of three cans of soft drinks of type 1, seven of type 2, none of ) ted Isor type 3, three of type 4, and two of type 5. The total number of selections of 15 cans of to odo of soft drinks of the five types is the number of strings of 19 symbols, 5-1= 4 of them| ed and 15 of them X: to 1odr (*)- 6 2 19.18 17 16 15! 15+5-1 19! (19) 15 151 -4-3-2-1 = 3,876. 15!·(19 – 15)! 15 b. If at least six cans of root beer are to be included in the selection, you can imagine choosing six such cans first and then choosing nine additional cans. The choice of the nine additional cans can be represented as a string of 9 ×'s and 4 's. For example, if root beer is type 1, then the string X × X || X X |X X X X | represents a selection of three cans of root beer (in addition to the six chosen initially), none of type 2. two of type 3, four of type 4, and none of type 5. Thus the total number of selections of 15 cans of soft drinks of the five types, including at least six cans of root beer, is the number of strings of 13 symbols, 4 (=5 – 1) of them | and 9 of them ×: 9+4 13 12-11 10-9! 91 -4-3-2-1 13! 13 9!-(13 – 9)! 9 = 715.
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