Practice city guilds model questions vol1 information_technology 2020 Past Questions

Question 1 View Details

A company has been allocated the network 192.168.48.0/20. It needs to create subnets for three departments requiring at least 1000, 500, and 200 host addresses respectively. Using variable length subnet masking (VLSM), determine the subnet mask (in dotted‑decimal notation) that must be assigned to the department needing 1000 hosts, and state the first usable IP address in that subnet.

A. 255.255.252.0; 192.168.48.5

B. 255.255.254.0; 192.168.48.1

C. 255.255.248.0; 192.168.48.1

Correct D. 255.255.252.0; 192.168.48.1

Correct Answer: D

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Question 2 View Details

A computer system has a cache that can be accessed in 5 ns and main memory that can be accessed in 80 ns. If the cache hit ratio is 0.9, calculate the average memory access time (in nanoseconds) experienced by the CPU.

Correct A. 13 ns

B. 14 ns

C. 12.5 ns

D. 5 ns

Correct Answer: A

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Question 3 View Details

Simplify the Boolean expression \( \overline{A}B + AB + \overline{A}\overline{B} \) to its minimal form.

A. \( \overline{A}B \)

B. \( A B \)

C. \( \overline{A}\overline{B} \)

Correct D. \( \overline{A} + B \)

Correct Answer: D

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Question 4 View Details

In a word‑processing task, each line can hold 65 characters and each page can accommodate 45 lines. A report contains a total of 27 300 characters (including spaces). Determine how many full pages are required to print the report and how many characters will appear on the final partially‑filled page.

A. 10 full pages; 0 characters on the last page

B. 8 full pages; 3900 characters on the last page

Correct C. 9 full pages; 975 characters on the last page

D. 9 full pages; 850 characters on the last page

Correct Answer: C

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Question 5 View Details

A 1500‑byte packet is transmitted over a 250‑km link whose propagation speed is \(2 \times 10^{8}\) m/s and whose bandwidth is 10 Mbps. The packet experiences a queuing delay of 2 ms at the source router. Compute the total time (in milliseconds) from the start of transmission until the last bit reaches the destination.

A. 3.80 ms

Correct B. 4.45 ms

C. 4.25 ms

D. 5.10 ms

Correct Answer: B

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Question 6 View Details

A school has 800 students distributed among four classes: A (200 students), B (180 students), C (150 students), and D (270 students). The proportion of students who use the internet daily is 70% in class A, 55% in class B, 40% in class C, and an unknown percentage \(x\) in class D. If overall 58% of all 800 students use the internet daily, determine the value of \(x\) (to one decimal place).

A. 58.3%

B. 59.9%

Correct C. 61.1%

D. 62.5%

Correct Answer: C

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Question 7 View Details

Consider the following pseudo‑code:\n\n``\ncount ← 0\nfor i ← 1 to n\n for j ← i to n\n if (i + j) mod 3 = 0 then\n count ← count + 1\n end if\n end for\nend for\noutput count\n``\n\nIf the input value is \(n = 10\), what integer does the program output?

A. 15

B. 12

C. 20

Correct D. 18

Correct Answer: D

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Question 8 View Details

An A4 document is formatted with the following specifications: page size 210 mm × 297 mm, margins 20 mm left/right and 25 mm top, 20 mm bottom. The text uses Times New Roman 12 pt font with 1.5 line spacing. The average character width is 2.5 mm and the average word (including a following space) occupies 6 characters. Determine how many sheets of paper are required to print a 12 000‑word report double‑sided.

Correct A. 14 sheets

B. 12 sheets

C. 15 sheets

D. 13 sheets

Correct Answer: A

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Question 9 View Details

A presentation consists of three sections.\n\n- Section A: 5 slides, each with 30 s narration followed by a 5 s transition.\n- Section B: twice as many slides as Section A, each slide having 45 s narration and a 4 s transition.\n- Section C: 4 slides, each with 20 s narration and a 6 s transition, followed by a video lasting 2 minutes.\n\nCalculate (a) the total duration of the presentation expressed in minutes and seconds, and (b) the total number of slides (excluding the video).

A. 13 minutes 55 seconds, 19 slides

Correct B. 14 minutes 49 seconds, 19 slides

C. 14 minutes 30 seconds, 18 slides

D. 15 minutes 10 seconds, 20 slides

Correct Answer: B

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Question 10 View Details

An organization is allocated the IPv4 block 192.168.48.0/22. It needs to create three sub‑nets for departments requiring at least 200 hosts, 50 hosts, and 10 hosts respectively. Using variable‑length subnet masking (VLSM), assign the smallest possible subnet mask to each department, give the network address of each subnet, and state the first usable IP address of the subnet that must accommodate at least 50 hosts.

Correct A. Subnet A: 192.168.48.0/24 (255.255.255.0)\nSubnet B: 192.168.49.0/26 (255.255.255.192) - first usable IP 192.168.49.1\nSubnet C: 192.168.49.64/28 (255.255.255.240)

B. Subnet A: 192.168.48.0/23 (255.255.254.0) Subnet B: 192.168.50.0/26 (255.255.255.192) - first usable IP 192.168.50.1 Subnet C: 192.168.50.64/28 (255.255.255.240)

C. Subnet A: 192.168.48.0/24 (255.255.255.0) Subnet B: 192.168.49.0/27 (255.255.255.224) - first usable IP 192.168.49.1 Subnet C: 192.168.49.32/28 (255.255.255.240)

D. Subnet A: 192.168.48.0/24 (255.255.255.0) Subnet B: 192.168.48.128/26 (255.255.255.192) - first usable IP 192.168.48.129 Subnet C: 192.168.48.192/28 (255.255.255.240)

Correct Answer: A

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Question 11 View Details

A secure system requires passwords that are exactly 8 characters long. Each character can be an uppercase letter (26 choices), a lowercase letter (26 choices), a digit (10 choices) or a symbol (12 choices). The policy mandates that a valid password must contain at least one uppercase letter, one lowercase letter, one digit and one symbol.\n\n(a) How many different passwords satisfy the policy? Express your answer in scientific notation to two decimal places.\n(b) What is the entropy of the password space in bits, rounded to the nearest whole number?\n(c) If an attacker can test \(10^{9}\) passwords per second, approximately how many days would it take to try half of the possible passwords?

A. ≈3.75×10^{14} passwords; 47 bits; about 3.1 days

Correct B. ≈4.09×10^{14} passwords; 49 bits; about 2.4 days

C. ≈5.20×10^{14} passwords; 51 bits; about 1.8 days

D. ≈4.09×10^{13} passwords; 49 bits; about 24 days

Correct Answer: B

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Question 12 View Details

A student prepares a report using Times New Roman 12‑pt font with 1.5 line spacing on A4 paper (21 cm × 29.7 cm). The margins are 2.5 cm on all sides. The average character width is 2.3 mm.\n\n(i) How many characters fit on one line?\n(ii) How many lines fit on one page?\n(iii) The document contains 125 000 characters (including spaces). How many whole pages are required for the text?\n(iv) The report also includes 5 figures that each occupy half a page and 3 tables that each occupy a full page. Taking these into account, what is the total number of pages to be printed?\n(v) The printing cost is ₦15 per page for the first 100 pages, ₦12 per page for the next 100 pages, and ₦10 per page thereafter. What is the total printing cost?

A. ₦945

Correct B. ₦810

C. ₦1,020

D. ₦750

Correct Answer: B

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Question 13 View Details

Three processes A, B and C are scheduled in the order A → B → C on a single‑CPU system. Their CPU bursts and I/O wait times are as follows:\n\n- Process A: CPU 20 ms, I/O wait 10 ms, then CPU 15 ms.\n- Process B: CPU 30 ms, I/O wait 5 ms, then CPU 20 ms.\n- Process C: CPU 25 ms, no I/O.\n\nAssume that while a process is performing I/O, the CPU can execute another ready process. Determine (i) the total elapsed time from the start of A to the completion of C, and (ii) the CPU utilisation percentage over this interval.

A. Total time 115 ms; CPU utilisation 95 %

Correct B. Total time 110 ms; CPU utilisation 100 %

C. Total time 110 ms; CPU utilisation 95 %

D. Total time 105 ms; CPU utilisation 100 %

Correct Answer: B

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Question 14 View Details

A company buys a machine for ₦500 000. Its estimated useful life is 5 years and the salvage value at the end of the period is ₦50 000. Using the double‑declining‑balance method, calculate the depreciation expense for year 3 and the cumulative depreciation after year 3.

A. Year 3 depreciation ₦80 000; cumulative depreciation ₦400 000

B. Year 3 depreciation ₦72 000; cumulative depreciation ₦380 000

Correct C. Year 3 depreciation ₦72 000; cumulative depreciation ₦392 000

D. Year 3 depreciation ₦70 000; cumulative depreciation ₦380 000

Correct Answer: C

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Question 15 View Details

In a spreadsheet, column B (cells B2:B21) holds the test scores of 20 students: 85, 73, 68, 59, 47, 92, 61, 55, 38, 77, 64, 49, 82, 71, 58, 45, 33, 69, 74, 52.\n\n(i) Write a formula for cell C2 that can be copied down to assign a letter grade according to the scheme: A ≥ 70, B = 60‑69, C = 50‑59, D = 40‑49, F < 40.\n(ii) Using that formula, how many students received each grade?

A. Formula: =IF(B2>=70,"A",IF(B2>=60,"B",IF(B2>=50,"C",IF(B2>=40,"D","F")))) ; Grades count - A:7, B:4, C:4, D:2, F:3

B. Formula: =IF(B2>=80,"A",IF(B2>=70,"B",IF(B2>=60,"C",IF(B2>=50,"D","F")))) ; Grades count - A:3, B:4, C:4, D:4, F:5

C. Formula: =IF(B2>=70,"A",IF(B2>=60,"B",IF(B2>=50,"C","F"))) ; Grades count - A:7, B:4, C:4, D:0, F:5

Correct D. Formula: =IF(B2>=70,"A",IF(B2>=60,"B",IF(B2>=50,"C",IF(B2>=40,"D","F")))) ; Grades count - A:7, B:4, C:4, D:3, F:2

Correct Answer: D

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Question 16 View Details

A client computer C is connected to Router R1 (10.0.0.1) via Ethernet. R1 connects to Router R2 (10.0.1.1) via a 100‑Mbps serial link, and R2 provides Internet access. The client can ping 8.8.8.8 with an average RTT of \(48\) ms and 0 % packet loss, but cannot resolve any domain name. When the client pings the DNS server at 10.0.0.53, the RTT is \(12\) ms with 30 % packet loss. When the client pings the web server at 93.184.216.34, the RTT is \(50\) ms with 0 % loss. Which component is most likely the cause of the failure? Give the most specific answer (e.g., "DNS server", "R1 interface", "serial link between R1 and R2").

A. R1 interface

B. R2 router

Correct C. DNS server

D. serial link between R1 and R2

Correct Answer: C

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Question 17 View Details

A company backs up three servers each night. Server A changes \(2\) GB per day, Server B changes \(5\) GB per day, and Server C changes \(1\) GB per day. The nightly backup window is \(4\) hours and the network transfer speed to the backup server is \(200\) Mbps. Choose a backup strategy that (i) fits within the backup window, (ii) minimises total storage needed for a 30‑day retention period, and (iii) provides the ability to restore any single day's data. State the strategy in one concise phrase (e.g., "weekly full with daily incremental").

A. monthly full with weekly incremental

B. daily full backup

C. weekly full with weekly incremental

Correct D. weekly full with daily incremental

Correct Answer: D

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Question 18 View Details

The following system log excerpts are recorded on a server. [10:15:23] INFO: Service X started. [10:15:45] WARN: Disk usage at 85%. [10:16:02] ERROR 0xC0000005: Access violation in process Y. [10:16:05] INFO: Attempting restart of Service X. [10:16:30] CRITICAL: System crash - kernel panic. Which logged event most directly triggered the system crash? Provide the exact log message (including the error code).

Correct A. [10:16:02] ERROR 0xC0000005: Access violation in process Y

B. [10:16:05] INFO: Attempting restart of Service X

C. [10:15:23] INFO: Service X started

D. [10:16:02] ERROR 0xC0000006: Access violation in process Y

Correct Answer: A

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Question 19 View Details

Consider the following pseudo‑code: ``` count = 0 for i in range(1, 6): # i = 1..5 for j in range(1, i+1): # j = 1..i if (i * j) % 3 == 0: count += 1 if count == 7: break if count == 7: break print(count) ``` What integer value is printed when the program is executed?

Correct A. 5

B. 4

C. 7

D. 6

Correct Answer: A

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Question 20 View Details

A network administrator is given the address block \(192.168.48.0/20\). Three departments need subnets for \(200\), \(50\) and \(10\) usable hosts respectively. Allocate subnets that minimise wasted addresses, and for each subnet provide (i) the subnet mask in dotted‑decimal form, and (ii) the first usable IP address. List the results in the order of the departments (200‑host, 50‑host, 10‑host).

A. 200‑host: 255.255.255.128, first usable 192.168.48.1; 50‑host: 255.255.255.192, first usable 192.168.49.1; 10‑host: 255.255.255.240, first usable 192.168.49.65

Correct B. 200‑host: 255.255.255.0, first usable 192.168.48.1; 50‑host: 255.255.255.192, first usable 192.168.49.1; 10‑host: 255.255.255.240, first usable 192.168.49.65

C. 200‑host: 255.255.255.0, first usable 192.168.48.1; 50‑host: 255.255.255.224, first usable 192.168.48.33; 10‑host: 255.255.255.240, first usable 192.168.49.65

D. 200‑host: 255.255.255.0, first usable 192.168.48.1; 50‑host: 255.255.255.192, first usable 192.168.49.33; 10‑host: 255.255.255.248, first usable 192.168.49.65

Correct Answer: B

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Question 21 View Details

A company has the network 192.168.0.0/24 and needs to create subnets for three departments requiring 50, 30, and 12 hosts respectively. Using VLSM, allocate the subnets in order of decreasing host requirement. What is the broadcast address of the subnet allocated to the department that requires 30 hosts?

Correct A. 192.168.0.95

B. 192.168.0.127

C. 192.168.0.63

D. 192.168.0.111

Correct Answer: A

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Question 22 View Details

Consider a relation R(A,B,C,D,E) with functional dependencies: A→B, B→C, C→D, D→E, and A→E. Identify the candidate key(s) and decompose R into Boyce‑Codd Normal Form (BCNF). How many relations result from the BCNF decomposition?

A. 6

B. 3

C. 5

Correct D. 4

Correct Answer: D

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Question 23 View Details

A RAID 5 array consists of 5 disks, each of capacity 2 TB and sequential read speed 200 MB/s. The annual failure probability of each disk is 0.02, independent of the others. What is the probability that the array suffers data loss due to two or more disk failures within a year? Express your answer as a decimal rounded to four significant figures.

A. 0.0062

Correct B. 0.0038

C. 0.0015

D. 0.0098

Correct Answer: B

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Question 24 View Details

A point‑to‑point link is 1500 km long. Signals travel at (2\times10^{8}\) m/s. The link bandwidth is 10 Mbps and a data packet of 1500 bytes is transmitted. Each router on the path adds a processing delay of 2 ms per packet. Assuming one router in each direction and that the ACK packet is negligible in size, calculate the total round‑trip time (RTT) in milliseconds. Then state whether the packet size exceeds the bandwidth‑delay product (answer "Yes" or "No").

Correct A. 20.2 ms, No

B. 20.2 ms, Yes

C. 18.5 ms, Yes

D. 22.7 ms, No

Correct Answer: A

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Question 25 View Details

A process is initially in the Ready state. The scheduler dispatches it, moving it to Running. After 5 seconds the process performs an I/O request and enters the Waiting state. When the I/O completes, the process returns to Ready. List the sequence of states the process passes through from the start until it is Ready again after the I/O.

A. Running → Waiting → Ready → Running

B. Ready → Waiting → Running → Ready

Correct C. Ready → Running → Waiting → Ready

D. Ready → Running → Ready → Waiting

Correct Answer: C

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