300-070 · Question #393
Which number is the result of applying phone number mask 1234X5XX to number 54321?
The correct answer is C. 12344521. A Cisco CUCM phone number mask right-aligns the original number beneath the mask pattern, with 'X' characters replaced by the corresponding digit from the aligned number and fixed digits kept as-is.
Question
Which number is the result of applying phone number mask 1234X5XX to number 54321?
Options
- A12354521
- B12344321
- C12344521
- D12355321
- E12354321
How the community answered
(17 responses)- B6% (1)
- C71% (12)
- D18% (3)
- E6% (1)
Why each option
A Cisco CUCM phone number mask right-aligns the original number beneath the mask pattern, with 'X' characters replaced by the corresponding digit from the aligned number and fixed digits kept as-is.
12354521 results from incorrectly substituting the first X with '5' instead of '4', which occurs when the number is not properly right-aligned before substitution.
12344321 incorrectly fills all X positions with consecutive digits from the number without respecting the fixed '5' digit at position 6 of the mask.
The mask '1234X5XX' is 8 characters long, so the 5-digit number '54321' is right-aligned beneath it as '___54321'. The fixed digits 1, 2, 3, 4, and 5 are retained in their positions, while the three X positions (5, 7, 8) pull the corresponding right-aligned digits (4, 2, 1), producing the result 12344521.
12355321 incorrectly places '5' into the first X position rather than the right-aligned digit '4' from the original number.
12354321 uses '5' for the first X position instead of the correct right-aligned digit '4', shifting all subsequent substituted digits incorrectly.
Concept tested: Cisco CUCM external phone number mask substitution
Source: https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/12_5_1/systemConfig/cucm_b_system-configuration-guide-1251/cucm_b_system-configuration-guide-1251_chapter_01001101.html
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