Practice city guilds model questions vol1 information_technology 2023 Past Questions

Question 1 View Details

A presenter has 20 slides. The first 5 slides are introductory and each takes \(45\) seconds. The next slides are content slides; the first content slide (slide 6) takes \(30\) seconds and each subsequent content slide takes twice as long as the previous one. The remaining slides are summary slides, each taking 1 minute. The whole presentation must not exceed 12 minutes. How many content slides can be included, and what is the total time actually used (express the time in minutes and seconds)?

A. 1 content slide; total time = 10 minutes 0 seconds

B. 2 content slides; total time = 10 minutes 45 seconds

Correct C. 2 content slides; total time = 11 minutes 15 seconds

D. 3 content slides; total time = 12 minutes 30 seconds

Correct Answer: C

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Question 2 View Details

An organisation protects its system with three security controls applied sequentially: a firewall, an intrusion‑detection system (IDS) and multi‑factor authentication (MFA). For an external attacker the probability of bypassing the firewall is \(0.02\). The IDS blocks an attack with probability \(0.95\) but has a false‑negative rate of \(10\%\). The MFA can be bypassed because of a system flaw with probability \(0.01\); if the flaw is not present the attacker can still guess the second factor correctly with probability \(0.30\). Assuming independence where appropriate, what is the overall probability that an attack successfully compromises the system? Give your answer as a percentage to three decimal places.

Correct A. 0.089%

B. 0.085%

C. 0.120%

D. 0.090%

Correct Answer: A

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Question 3 View Details

A signed 8‑bit integer is stored in two's‑complement form. The bit pattern shown is \(1110\;0111\). What decimal integer does this pattern represent?

Correct A. -25

B. 25

C. -24

D. -26

Correct Answer: A

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Question 4 View Details

Consider a relation \(R(A,B,C,D)\) with the functional dependencies \(A \rightarrow B\), \(BC \rightarrow D\) and \(D \rightarrow A\).\n\n(a) List all candidate keys of \(R\).\n\n(b) State the highest normal form (up to BCNF) that \(R\) satisfies, justifying your answer.

A. Candidate keys: AC, BC. Highest normal form: 3NF (not BCNF).

B. Candidate keys: AC, BC, CD. Highest normal form: BCNF.

C. Candidate keys: AB, AD, CD. Highest normal form: 2NF.

Correct D. Candidate keys: AC, BC, CD. Highest normal form: 3NF (not BCNF).

Correct Answer: D

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Question 5 View Details

A presenter wants the file size of a 30‑slide presentation to be at most \(50\) MB. Each slide can contain either an image, a video clip, or plain text. The average sizes are: image \(0.8\) MB, video \(5\) MB, text \(0.05\) MB (considered negligible). The presenter decides to include exactly twice as many image slides as video slides, and the remaining slides are text slides. What is the greatest possible number of video slides that can be used without exceeding the size limit, and what is the resulting total file size (in MB, rounded to two decimal places)?

A. Maximum video slides = 8; total size = 53.10 MB

Correct B. Maximum video slides = 7; total size = 46.65 MB

C. Maximum video slides = 5; total size = 33.75 MB

D. Maximum video slides = 6; total size = 40.20 MB

Correct Answer: B

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Question 6 View Details

A small office network uses the subnet (192.168.1.0/24) with default gateway (192.168.1.1) and DNS server (8.8.8.8). Five PCs (A-E) have the configurations shown: - PC A: IP (192.168.1.10), MAC ...EE:02 - PC B: IP (192.168.1.21), MAC ...EE:03 - PC C: IP (192.168.1.32), MAC ...EE:04 - PC D: IP (192.168.1.45), MAC ...EE:05 - PC E: IP (192.168.1.58), MAC ...EE:06 A firewall rule blocks traffic from any PC whose last octet of the IP address is odd **unless** the last hexadecimal digit of its MAC address is even (0,2,4,6,8,A,C,E). All other PCs can access the Internet. Which PCs are able to browse the Internet?

A. PC A, PC B and PC C

B. PC A, PC B and PC D

C. PC B, PC D and PC E

Correct D. PC A, PC C and PC E

Correct Answer: D

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Question 7 View Details

Consider the following pseudo‑code where (N = 30\): ``` int sum = 0; for (int i = 2; i <= N; i++) { // test primality of i bool isPrime = true; for (int d = 2; d*d <= i; d++) { if (i % d == 0) { isPrime = false; break; } } if (isPrime) { // compute digit sum of i int temp = i, digitSum = 0; while (temp > 0) { digitSum += temp % 10; temp /= 10; } if (digitSum % 3 == 0) { sum += i; } } } print(sum); ``` What integer value is printed?

Correct A. 3

B. 9

C. 6

D. 0

Correct Answer: A

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Question 8 View Details

Four processes arrive for CPU scheduling as shown (times in milliseconds). The scheduler uses **pre‑emptive priority scheduling** where a higher numeric priority pre‑empts a lower one; if priorities are equal, the earlier‑arriving process runs first. | Process | Arrival | Burst | Priority | |---------|---------|-------|----------| | P1 | 0 | 8 | 2 | | P2 | 1 | 4 | 3 | | P3 | 2 | 9 | 1 | | P4 | 3 | 5 | 2 | Calculate the **average waiting time** of the four processes. (Waiting time = total time a process spends in the ready queue.)

A. 5 ms

B. 12 ms

Correct C. 7 ms

D. 9 ms

Correct Answer: C

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Question 9 View Details

A 120‑page document contains 500 words per page. The average word length is 5 characters and there is one space between consecutive words. The document also includes 30 images (each 150 KB) and 5 tables (each 20 KB). The file is first saved as a .docx (no compression) and then exported to PDF. In the PDF, text is compressed to 30 % of its original size, images to 50 %, and tables to 70 %. Calculate the size of the final PDF file in megabytes (MB), rounded to two decimal places. (1 KB = 1024 bytes, 1 MB = 1024 KB.)

A. 3.12 MB

Correct B. 2.37 MB

C. 2.90 MB

D. 1.85 MB

Correct Answer: B

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Question 10 View Details

A document contains headings of three levels. The counts are: - Level 1 headings: 8 - Level 2 headings: 15 - Level 3 headings: 22 When generating a Table of Contents, the style includes all Level 1 and Level 2 headings but omits Level 3 entries. How many entries will appear in the Table of Contents?

A. 30

B. 22

C. 15

Correct D. 23

Correct Answer: D

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Question 11 View Details

A spreadsheet records monthly sales in cells B2 to B6 for January to May respectively. The values are: B2 = 45 000, B3 = ?, B4 = 55 000, B5 = ?, B6 = 60 000. Cell B7 contains the formula ( =\text{SUM}(B2:B6) \) and the target total for the five months is 250 000. If the sales for February (B3) and April (B5) are equal, determine the sales figure for each of those two months.

A. 40000

B. 50000

C. 42500

Correct D. 45000

Correct Answer: D

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Question 12 View Details

In a computer system a text file contains 3 200 characters. 80 % of the characters are standard ASCII and are stored using 1 byte each in UTF‑8. The remaining characters require 2 bytes each. Calculate the total storage size of the file in bytes.

A. 3520

B. 3200

C. 4480

Correct D. 3840

Correct Answer: D

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Question 13 View Details

An organization uses three independent security layers to detect cyber‑attacks. For attack type A (which occurs 60 % of the time) the detection probabilities are: firewall 0.9, IDS 0.85, backup measure 0.6. For attack type B (occurs 40 % of the time) the detection probabilities are: firewall 0.7, IDS 0.75, backup measure 0.5. Assuming the layers operate independently, what is the overall probability that a randomly occurring attack is detected by at least one layer? Give your answer to four decimal places.

A. 0.9714

Correct B. 0.9814

C. 0.9810

D. 0.9874

Correct Answer: B

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Question 14 View Details

Consider the recursive function defined for non‑negative integers: \[ f(n)=\begin{cases} 1, & n\le 1\\[2mm] f(n-1)+2\,f(n-2), & n>1 \end{cases} \] (a) Compute the value of \(f(5)\). (b) State the asymptotic time‑complexity of a naïve implementation that follows this definition, using big‑O notation.

A. f(5)=19; time complexity O(2^n)

B. f(5)=23; time complexity O(2^n)

C. f(5)=21; time complexity O(n^2)

Correct D. f(5)=21; time complexity O(2^n)

Correct Answer: D

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Question 15 View Details

An IPv4 address is 172.20.45.130 with a subnet mask of /21. Determine (i) the network address, (ii) the broadcast address, and (iii) the number of usable host addresses in this subnet.

Correct A. Network address: 172.20.40.0, Broadcast address: 172.20.47.255, Usable hosts: 2046

B. Network address: 172.20.40.0, Broadcast address: 172.20.47.255, Usable hosts: 4094

C. Network address: 172.20.32.0, Broadcast address: 172.20.39.255, Usable hosts: 2046

D. Network address: 172.20.40.0, Broadcast address: 172.20.47.254, Usable hosts: 2046

Correct Answer: A

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Question 16 View Details

A company has been allocated the address block 10.0.0.0/16. It needs to create at least 200 subnets, each of which must support a minimum of 50 usable host addresses. Determine the most efficient subnet mask (i.e., the longest prefix length) that satisfies both requirements and state the number of usable host addresses per subnet.

A. Subnet mask 255.255.255.224 (/27); 30 usable hosts per subnet

Correct B. Subnet mask 255.255.255.192 (/26); 62 usable hosts per subnet

C. Subnet mask 255.255.255.0 (/24); 254 usable hosts per subnet

D. Subnet mask 255.255.255.128 (/25); 126 usable hosts per subnet

Correct Answer: B

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Question 17 View Details

Consider the relational schema: - Employees(EmpID, DeptID, Salary) - 500 rows - Departments(DeptID, ManagerID) - 20 rows - Projects(ProjID, DeptID) - 80 rows - WorksOn(EmpID, ProjID, Hours) - 1500 rows Selectivity of the condition Salary > 50000 on Employees is 0.2 and selectivity of Hours > 10 on WorksOn is 0.3. Write a relational‑algebra expression that returns the EmpID of employees who (i) have Salary > 50000, (ii) work on a project where Hours > 10, and (iii) the project belongs to the same department as the employee. Estimate the number of resulting rows assuming a join order that minimises intermediate result sizes.

Correct A. Approximately 5 rows (employee IDs)

B. Approximately 12 rows (employee IDs)

C. Approximately 2 rows (employee IDs)

D. Approximately 20 rows (employee IDs)

Correct Answer: A

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Question 18 View Details

Four processes have CPU burst times (in milliseconds) as follows: P1 = 6 ms, P2 = 8 ms, P3 = 7 ms, P4 = 3 ms. Compute the average waiting time for (a) First‑Come‑First‑Served (FCFS) and (b) non‑preemptive Shortest‑Job‑First (SJF). Which algorithm yields the lower average waiting time?

A. FCFS average waiting time = 11 ms; SJF average waiting time = 7 ms; FCFS is lower

B. FCFS average waiting time = 9.75 ms; SJF average waiting time = 8 ms; SJF is lower

C. FCFS average waiting time = 10.25 ms; SJF average waiting time = 6 ms; SJF is lower

Correct D. FCFS average waiting time = 10.25 ms; SJF average waiting time = 7 ms; SJF is lower

Correct Answer: D

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Question 19 View Details

A TCP connection starts with a congestion window (cwnd) of 1 MSS and a slow‑start threshold (ssthresh) of 8 MSS. No packet loss occurs. The sender receives acknowledgments for a total of 12 MSS of data. During slow start the cwnd doubles each round‑trip time (RTT); after cwnd reaches ssthresh it enters congestion avoidance, where cwnd increases by 1 MSS per RTT. Determine the value of cwnd (in MSS) after the 12th ACK has been received and indicate in which phase (slow start or congestion avoidance) each RTT occurs.

A. cwnd = 7 MSS after the 12th ACK; RTT 1‑3 slow start, RTT 4 congestion avoidance

Correct B. cwnd = 8 MSS after the 12th ACK; RTT 1‑3 slow start, RTT 4 congestion avoidance

C. cwnd = 9 MSS after the 12th ACK; RTT 1‑3 slow start, RTT 4 congestion avoidance

D. cwnd = 8 MSS after the 12th ACK; RTT 1‑2 slow start, RTT 3‑4 congestion avoidance

Correct Answer: B

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Question 20 View Details

A password policy requires exactly 6 characters. Each character can be chosen from four categories: 2 uppercase letters, 2 lowercase letters, 2 digits, and 2 symbols. A valid password must contain **at least one** character from each category. (a) How many distinct passwords satisfy the policy? (b) If an attacker guesses passwords uniformly at random, what is the probability that the correct password is found within the first 10 attempts?

A. a) 99,840 passwords; b) probability = 1\/9,984 ≈ 0.0002004

Correct B. a) 99,840 passwords; b) probability = 1/9,984 ≈ 0.0001002

C. a) 98,560 passwords; b) probability = 1\/9,856 ≈ 0.0001015

D. a) 100,800 passwords; b) probability = 1\/10,080 ≈ 0.0000992

Correct Answer: B

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Question 21 View Details

In a spreadsheet, column A contains Quantity, column B contains Unit Price, column C contains Discount % (applied as a decimal), and column D calculates the Total using the formula \(=A5*B5*(1-C5)\). For row 5 the Quantity entered is 250. The Unit Price should be obtained from a VLOOKUP that returns \(8.75\), but it was mistakenly entered as \(9.25\). The Discount % is determined by an IF formula: if Quantity > 200 then 12 % else 5 %. The Total cell currently shows \(2035\). What should be the correct Total for row 5, and what is the discrepancy between the displayed Total and the correct Total?

A. 2025.00, 10.00

B. 1900.00, 135.00

C. 1975.00, 60.00

Correct D. 1925.00, 110.00

Correct Answer: D

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Question 22 View Details

A user cannot open the website www.example.com. The following diagnostics are recorded: - Ping to 8.8.8.8: average 32 ms, 0 % packet loss. - Ping to the website's IP (93.184.216.34): average 150 ms, 20 % packet loss. - nslookup of www.example.com returns the IP 93.184.216.34. - Traceroute to the website shows a delay of 200 ms at hop 3. The network firewall blocks TCP port 80 for any MAC address not listed in its allowed‑MAC table, and the user's MAC address is currently absent from that list. Assuming each remedial step (adding the MAC address to the firewall, clearing the DNS cache, and restarting the NIC) takes exactly 2 minutes, identify the most probable cause of the problem and calculate the minimum total time required to restore access.

A. DNS cache issue; 4 minutes

B. Incorrect IP address; 6 minutes

C. Network latency; 2 minutes

Correct D. Firewall MAC‑address block; 6 minutes

Correct Answer: D

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Question 23 View Details

A network uses the address block \(192.168.48.0/20\). The administrator must create subnets that each support at least 500 usable host addresses. Determine: (a) the new subnet mask in CIDR notation, (b) the total number of subnets that can be created, and (c) the first usable IP address of the third subnet (counting from the first subnet).

A. /23, 8, 192.168.48.1

Correct B. /23, 8, 192.168.52.1

C. /23, 4, 192.168.56.1

D. /24, 16, 192.168.52.1

Correct Answer: B

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Question 24 View Details

A system stores passwords as SHA‑256 hashes. An attacker can compute \(5\times10^{9}\) hashes per second. The password policy requires passwords of exactly 8 characters, each character being an uppercase letter (26), a lowercase letter (26) or a digit (10).\ (a) Calculate the total number of possible passwords and the time (in hours) required for the attacker to exhaust the entire key space. (b) The security policy states that the time to brute‑force a password must exceed 100 years. Does the current 8‑character policy satisfy this requirement? If not, what is the minimum password length (still using the same 62‑character set) that meets the 100‑year threshold?

A. a) 218,340,105,584,896 passwords; ≈24.26 hours. b) Yes; minimum length = 8 characters.

B. a) 218,340,105,584,896 passwords; ≈12.13 hours. b) No; minimum length = 10 characters.

Correct C. a) 218,340,105,584,896 passwords; ≈12.13 hours. b) No; minimum length = 11 characters.

D. a) 218,340,105,584,896 passwords; ≈6.07 hours. b) No; minimum length = 12 characters.

Correct Answer: C

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Question 25 View Details

Consider the following pseudocode: ``` count ← 0 for i ← 1 to n do for j ← 1 to i do if (i × j) mod 3 = 0 then count ← count + 1 end if end for end for ``` If \(n = 10\), what is the final value of **count**? Also state the time‑complexity of the algorithm in Big‑O notation.

A. 27; O(n^3)

B. 30; O(n^2)

Correct C. 27; O(n^2)

D. 24; O(n log n)

Correct Answer: C

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