Practice city guilds model questions vol1 information_technology 2025 Past Questions

Question 1 View Details

A 12 MB file is to be transferred over a network using TCP. Each TCP segment carries a payload of 1460 bytes, and each IP packet adds a 20‑byte IP header and a 20‑byte TCP header. The link has a bandwidth of 100 Mbps and a round‑trip time (RTT) of 80 ms. Assuming the TCP window size is large enough to keep the link fully utilized and that the transmission starts with a three‑way handshake (which adds one RTT) and ends with a four‑way termination (adds another RTT), calculate the total time required to transfer the file, ignoring any retransmissions. Give your answer in seconds to two decimal places.

A. 1.00

B. 1.40

C. 0.96

Correct D. 1.20

Correct Answer: D

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Question 2 View Details

In an office network, a PC (PC1) cannot access the internet. The layout is PC1 → Switch A (IP 192.168.1.2) → Router R (IP 192.168.1.1) → ISP gateway. Observations:\n- PC1 pings Switch A with an RTT of 2 ms.\n- PC1 cannot ping Router R (request times out).\n- A second PC (PC2) on the same switch pings Router R successfully with an RTT of 3 ms.\n- A traceroute from PC1 to 8.8.8.8 shows the first hop as 192.168.1.2 and then stops.\n- The LED on Switch A's port to the router is amber (link error), while the port to PC1 is green.\nAssuming all IP settings are correct and the router's firewall is disabled, identify the most likely faulty component and justify your answer.

Correct A. The link (cable or switch port) between Switch A and Router R is faulty.

B. Switch A has a misconfigured VLAN that prevents communication with Router R.

C. The firewall on Router R is blocking ICMP traffic.

D. The IP address configuration on PC1 is incorrect.

Correct Answer: A

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Question 3 View Details

A spreadsheet records monthly sales (in thousands) for three products A, B, C over six months (Jan-Jun) in the range B2:D7 (rows = months, columns = products). The company defines a monthly performance index as\n\[ Performance = \bigl(0.5\times\frac{A}{\text{total}} + 0.3\times\frac{B}{\text{total}} + 0.2\times\frac{C}{\text{total}}\bigr)\times100 \]\nwhere "total" is the sum of A, B and C for that month.\n\n(a) Write a single Excel formula that can be entered in cell E2 and copied down to compute the performance index for each month without using helper columns.\n(b) Using the data below, calculate the performance index for March (row 4) and give the result rounded to two decimal places.\n\nData (in thousands):\nJan - A=120, B=80, C=50\nFeb - A=150, B=90, C=60\nMar - A=130, B=110, C=70\nApr - A=140, B=100, C=80\nMay - A=160, B=120, C=90\nJun - A=170, B=130, C=100

A. 32.75

Correct B. 36.13

C. 34.56

D. 38.90

Correct Answer: B

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Question 4 View Details

Consider the following pseudo‑code function that operates on a positive integer n:\n\n``` function mystery(n): if n = 1 then return 1 else if n is even then return mystery(n/2) + mystery(n/2 + 1) else return 2 * mystery((n-1)/2) ```\n\n(a) Compute the value returned by `mystery(7)`.\n(b) Prove briefly that for every positive integer n, `mystery(n) = n`. Provide the answer for part (a) and a concise justification for part (b).

A. 5

B. 3

C. 6

Correct D. 4

Correct Answer: D

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Question 5 View Details

A relation R(A, B, C, D, E) has the following functional dependencies:\n\n1. $A \rightarrow B C$\n2. $B D \rightarrow E$\n3. $C \rightarrow D$\n4. $E \rightarrow A$\n\n(a) List all candidate keys of R.\n(b) Decompose R into a collection of relations that are in Boyce‑Codd Normal Form (BCNF) using the synthesis algorithm, and state the resulting relation schemas.\n(c) For the original relation R, state the highest normal form it satisfies (1NF, 2NF, 3NF, BCNF) and justify your answer.

A. Candidate keys: A, E, BC, BD. BCNF decomposition: R1(C,D), R21(A,B,C), R22(A,E). Highest normal form: BCNF.

B. Candidate keys: A, E, BC, BD. BCNF decomposition: R1(A,B), R2(C,D), R3(B,E). Highest normal form: 3NF.

Correct C. Candidate keys: A, E, BC, BD. BCNF decomposition: R1(C,D), R21(A,B,C), R22(A,E). Highest normal form: 1NF.

D. Candidate keys: A, C, BD, CE. BCNF decomposition: R1(C,D), R21(A,B,C), R22(A,E). Highest normal form: 2NF.

Correct Answer: C

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Question 6 View Details

A computer stores unsigned integers in binary. What is the minimum number of bits required to represent all decimal numbers from 0 up to and including 150?

A. 9

Correct B. 8

C. 6

D. 7

Correct Answer: B

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Question 7 View Details

A network 192.168.48.0/24 must be divided into subnets that each support at least 30 usable host addresses and all subnets must be of equal size. Determine (a) the subnet mask to use, (b) the total number of subnets created, and (c) the range of usable host addresses in the first subnet.

Correct A. Subnet mask /27; 8 subnets; first subnet hosts 192.168.48.1 - 192.168.48.30

B. Subnet mask \/26; 4 subnets; first subnet hosts 192.168.48.1 - 192.168.48.62

C. Subnet mask \/28; 16 subnets; first subnet hosts 192.168.48.1 - 192.168.48.14

D. Subnet mask \/27; 6 subnets; first subnet hosts 192.168.48.1 - 192.168.48.30

Correct Answer: A

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Question 8 View Details

Consider a relation R(A, B, C, D) with the functional dependencies: $A \rightarrow B$, $B \rightarrow C$, $A \rightarrow D$.\n(a) List all candidate keys of R.\n(b) State the highest normal form (1NF, 2NF, 3NF, BCNF) that R satisfies.\n(c) Provide a lossless, dependency‑preserving decomposition of R into BCNF relations.

A. Candidate key: {A}. Highest normal form: 3NF. BCNF decomposition: R1(A, B, C) and R2(A, D).

Correct B. Candidate key: {A}. Highest normal form: 2NF. BCNF decomposition: R1(B, C) and R2(A, B, D).

C. Candidate key: {A, B}. Highest normal form: 3NF. BCNF decomposition: R1(A, B) and R2(B, C, D).

D. Candidate key: {B}. Highest normal form: 2NF. BCNF decomposition: R1(B, C) and R2(A, D).

Correct Answer: B

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Question 9 View Details

A document is typed in Times New Roman 12‑pt font with 1.5 line spacing on A4 paper (210 mm × 297 mm). The margins are 25 mm top and bottom, 20 mm left and right. The average word consists of 5 characters plus a space (6 characters). Each character occupies 2.3 mm width on average. How many pages are required to print a 12 000‑word document?

A. 30

B. 25

C. 24

Correct D. 27

Correct Answer: D

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Question 10 View Details

In a typical operating system a process can be in one of five states: New, Ready, Running, Waiting, Terminated. If a process is currently in the Waiting state, list the possible states it can transition to next.

A. Ready or Running

Correct B. Ready or Terminated

C. New or Terminated

D. Running or Terminated

Correct Answer: B

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Question 11 View Details

Consider the following pseudocode: ``` count = 0 for i = 1 to n for j = i to n if (i + j) mod 3 = 0 then count = count + 1 end if end for end for ``` If $n = 12$, what is the final value of **count**?

A. 30

B. 24

C. 28

Correct D. 26

Correct Answer: D

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Question 12 View Details

A company records its monthly revenue and cost for a 12‑month fiscal year. - Revenue follows an arithmetic progression: $R_m = 8000 + 500\,(m-1)$ naira for month $m$ ($m=1$ to $12$). - Cost follows a geometric progression: $C_m = 3000\times 1.05^{\,m-1}$ naira. - Profit for a month is $P_m = R_m - C_m$. - If a month's profit exceeds $5{,}000$ naira, a tax of 10 % is deducted from that month's profit; otherwise no tax is applied. Calculate the total net profit for the year, rounded to the nearest naira.

Correct A. 73624

B. 74624

C. 73524

D. 72624

Correct Answer: A

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Question 13 View Details

A password must be exactly six characters long. The allowed characters are: - Upper‑case letters: $A$-$E$ (5 choices) - Lower‑case letters: $a$-$e$ (5 choices) - Digits: $0$-$3$ (4 choices) - Special symbols: $!$ and $@$ (2 choices) The policy requires **at least one upper‑case letter**, **at least one digit**, and **no more than one special symbol**. How many different passwords satisfy the policy?

A. 10696520

Correct B. 10596520

C. 11596520

D. 1059652

Correct Answer: B

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Question 14 View Details

Four processes arrive at a CPU as shown below (times are in milliseconds). The CPU uses the **Shortest Remaining Time First (SRTF)** pre‑emptive scheduling algorithm. | Process | Arrival Time | CPU Burst | |---------|--------------|-----------| | P1 | 0 | 8 | | P2 | 1 | 4 | | P3 | 2 | 9 | | P4 | 3 | 5 | For each process, compute its **turnaround time** (completion time $-$ arrival time) and then give the **average turnaround time** for the four processes.

A. 15

B. 14

Correct C. 13

D. 12

Correct Answer: C

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Question 15 View Details

An office network is configured as follows: - Main LAN: subnet $192.168.10.0/24$ with a router that provides DHCP addresses $192.168.10.50$-$192.168.10.100$. - A network printer has the static address $192.168.10.20$. - A separate Wi‑Fi VLAN uses subnet $192.168.20.0/24$; the router's interface on this VLAN is $192.168.20.1$. - The router performs NAT only for traffic originating from $192.168.10.0/24$. A user connected to the Wi‑Fi VLAN can ping the router ($192.168.20.1$) but cannot ping the external address $8.8.8.8$. DNS is correctly configured. What is the most probable cause of the problem? Provide a short phrase describing the cause.

A. Incorrect default gateway set for Wi‑Fi clients (192.168.20.0/24)

B. DHCP range exhausted on the Wi‑Fi VLAN (192.168.20.0/24)

Correct C. NAT not configured for the Wi‑Fi VLAN (192.168.20.0/24)

D. Firewall blocks outbound traffic from the Wi‑Fi VLAN (192.168.20.0/24)

Correct Answer: C

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Question 16 View Details

A file contains $3,200$ characters, each stored as one byte. If $1$ kilobyte $=$ $1,024$ bytes, what is the minimum whole number of kilobytes required to store the file?

A. 5 KB

B. 3 KB

Correct C. 4 KB

D. 6 KB

Correct Answer: C

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Question 17 View Details

In a typical operating system, a process can be in one of four states: Ready, Running, Waiting, or Terminated. Suppose a particular process spends $30$ seconds in the Ready state, $45$ seconds in the Running state, and $20$ seconds in the Waiting state before terminating. How many seconds of CPU time does the process actually use?

A. 95 seconds

Correct B. 45 seconds

C. 30 seconds

D. 20 seconds

Correct Answer: B

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Question 18 View Details

An organization has been allocated the IPv4 address block $192.168.64.0/20$. They need to create subnets that can each accommodate up to $500$ hosts (two addresses per subnet are reserved for network and broadcast). Determine the smallest possible subnet mask that satisfies this requirement and state how many such subnets can be obtained from the original $/20$ block.

Correct A. /23, 8 subnets

B. /24, 4 subnets

C. /22, 16 subnets

D. /25, 8 subnets

Correct Answer: A

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Question 19 View Details

A security policy requires passwords to be exactly $12$ characters long. Each character may be an uppercase letter (26 choices), a lowercase letter (26 choices), a digit (10 choices), or one of $12$ special symbols. The policy also mandates that every password contain at least one digit and at least one special symbol. (a) How many distinct passwords satisfy the policy? (b) If an attacker can test $10^{9}$ passwords per second, what is the minimum time in years required to exhaust the entire password space? (Give your answer rounded to two significant figures.)

A. a) $74^{12} - 64^{12} - 62^{12} + 52^{12}$ ≈ 1.5×10^22 passwords; b) ≈ 6.1×10^4 years

Correct B. a) $74^{12} - 64^{12} - 62^{12} + 52^{12}$ ≈ 1.9×10^22 passwords; b) ≈ 6.1×10^5 years

C. a) $74^{12} - 64^{12} - 62^{12} + 52^{12}$ ≈ 1.9×10^22 passwords; b) ≈ 5.0×10^5 years

D. a) $74^{12} - 64^{12} - 62^{12} + 52^{12}$ ≈ 2.3×10^22 passwords; b) ≈ 7.5×10^5 years

Correct Answer: B

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Question 20 View Details

A system has two resource types, A and B, with total quantities $10$ and $7$ respectively. The current allocation and maximum demand matrices for three processes are: \[ \begin{array}{c|ccc} & P1 & P2 & P3 \\ \hline \text{Allocation} & (2,1) & (3,2) & (2,1) \\ \text{Maximum} & (5,3) & (3,5) & (5,3) \\ \end{array} \] Using the Banker's algorithm, determine whether the system is in a safe state. If it is safe, give one possible safe sequence of process execution.

A. Safe state; safe sequence P2 → P3 → P1

B. Safe state; safe sequence P1 → P2 → P3

C. Unsafe state; no safe sequence

Correct D. Safe state; safe sequence P2 → P1 → P3

Correct Answer: D

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Question 21 View Details

Consider the following pseudo‑code: ``` integer n = 5 integer total = 0 for i = 1 to n for j = i to n if ( (i*j) \bmod 3 = 0 ) total = total + i - j else total = total + j - i end if end for end for output total ``` What value is displayed when the program finishes execution?

A. 6

B. 10

C. 12

Correct D. 8

Correct Answer: D

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Question 22 View Details

A relation STUDENT(SID, Name, Dept, Advisor, AdvisorPhone) is subject to the functional dependencies:\n\n$\text{SID} \rightarrow \text{Name}, \text{Dept}, \text{Advisor}$\n$\text{Advisor} \rightarrow \text{AdvisorPhone}$\n$\text{Dept} \rightarrow \text{Advisor}$\n\nDetermine a lossless‑decomposition of STUDENT into relations that are in Third Normal Form (3NF). List each resulting relation schema.

A. STUDENT1(SID, Name, Advisor), DEPT(Dept), ADVISOR_PHONE(Advisor, AdvisorPhone)

B. STUDENT1(SID, Name), DEPT_ADVISOR(Dept, Advisor, AdvisorPhone)

C. STUDENT(SID, Name, Dept, Advisor), ADVISOR_PHONE(Advisor, AdvisorPhone)

Correct D. STUDENT1(SID, Name, Dept), DEPT_ADVISOR(Dept, Advisor), ADVISOR_PHONE(Advisor, AdvisorPhone)

Correct Answer: D

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Question 23 View Details

In a spreadsheet the following data and formulas are entered:\n\n- Cells $A1$ to $A4$ contain the quantities 4, 5, 6, 7 respectively.\n- Cells $B1$ to $B4$ contain the unit prices 10, 12, 9, 11 respectively.\n- Cell $C1$ contains the formula $=A1 \times B1$. Cells $C2$ to $C4$ are obtained by copying the formula in $C1$ down the column.\n- Cell $E1$ contains the constant discount factor 0.9.\n- Cell $F1$ contains the formula $=C1 \times \$E\$1$. Cells $F2$ to $F4$ are obtained by copying the formula in $F1$ down the column.\n- Cell $G1$ contains the formula $=SUM(F1:F4)$.\n\nWhat numeric value is displayed in cell $G1$ after all formulas are evaluated? (Give your answer to one decimal place.)

A. 231.0

Correct B. 207.9

C. 208.9

D. 184.8

Correct Answer: B

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Question 24 View Details

Convert the decimal integer 156 to its binary representation.

Correct A. 10011100

B. 10011011

C. 10011101

D. 10100100

Correct Answer: A

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Question 25 View Details

An organization has been allocated the IPv4 address block 192.168.48.0/20. It needs to create subnets, each of which must support at least 500 usable host addresses.\n\na) What subnet mask should be used for these subnets?\nb) How many such subnets can be created from the given /20 block?\nc) What is the network address of the first subnet?

A. Subnet mask 255.255.252.0; number of subnets 4; first subnet 192.168.48.0/22

B. Subnet mask 255.255.255.0; number of subnets 16; first subnet 192.168.48.0/24

Correct C. Subnet mask 255.255.254.0; number of subnets 8; first subnet 192.168.48.0/23

D. Subnet mask 255.255.254.0; number of subnets 6; first subnet 192.168.48.0/23

Correct Answer: C

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