ITPEC IP October 2020 Question 32
ITPEC IP October 2020 — Question 32 of 100
Thirteen digits are required. After the fixed prefix 020, the first variable digit has eight allowed choices: 1, 2, 3, and 5 through 9. To create eight billion numbers, the remaining variable positions must supply one billion combinations, requiring nine decimal digits because 10⁹ = 1,000,000,000. Thus the total is 3 + 1 + 9 = 13.
Answer (c)
Why not others:
- 11 and 12 digits provide too few combinations
- 14 digits would provide more capacity than the minimum required
Key rule: Multiply the number of choices at each position, and include all fixed prefix digits when reporting total length.
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