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Sagot :
Answer:
(a) 2,358,720,000
(b) 676,000,000,000
(c) 420,000,000,000
Step-by-step explanation:
The serial number on a bill consists of a letter followed by nine digits and then a letter.
There are 26 different letters and 10 digits (0 through 9) available.
Part (a)
If the letters and digits cannot be repeated, there are:
- 26 choices for the first letter and 25 choices for the second letter.
- 10 choices for the first digit, 9 choices for the second digit, 8 choices for the third digit, and so on.
Therefore, the number of serial numbers that are possible if the letter and digits cannot be repeated is:
26 × 10 × 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 25 = 2,358,720,000
Part (b)
If the letters and digits can be repeated, there are:
- 26 choices for each letter.
- 10 choices for each digit.
Therefore, the number of serial numbers that are possible if the letter and digits can be repeated is:
26 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 26 = 676,000,000,000
Part (c)
There are 21 consonants in the alphabet.
If the letters are non-repeated consonants and the digits can be repeated, there are:
- 21 choices for the first letter and 20 choices for the second letter.
- 10 choices for each digit.
Therefore, the number of serial numbers that are possible if the letters are non-repeated consonants and the digits can be repeated is:
21 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 20 = 420,000,000,000
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