Practice city guilds model questions vol1 information_technology 2019 Past Questions

Question 1 View Details

A secure web service enforces the following password policy: passwords must be exactly $8$ characters long and each character can be an uppercase letter (26), a lowercase letter (26), a digit (10) or one of $10$ allowed special symbols, giving $72$ possible symbols per position. The system locks an account for $15$ minutes after $5$ consecutive failed login attempts; the lockout timer resets after the lockout period. An attacker can try $1000$ guesses per second but is limited by the lockout policy. Assuming users choose passwords uniformly at random from the allowed set, estimate the average time (in years) required for the attacker to compromise a single account. Then, if the attacker targets $100$ different accounts simultaneously, what is the new average time to compromise any one of them? Give your final answer for the $100$-account scenario, rounded to two significant figures.

A. approximately 2.1\times10^{6} years

B. approximately 3.0\times10^{7} years

Correct C. approximately 2.1\times10^{7} years

D. approximately 1.5\times10^{7} years

Correct Answer: C

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Question 2 View Details

A 30‑slide presentation is being prepared. Each slide uses a background image of resolution $1920\times1080$ pixels, stored in PNG format with an average compression ratio of $3:1$. Each pixel is stored with 24‑bit colour. Apart from the background, every slide contains $200$ bytes of text and two animations, each requiring $500$ bytes. Ten of the slides share the same background image, while the remaining slides each have a unique background image. The total file size must not exceed $5$ MiB ($5\times1024\times1024$ bytes). What is the maximum number of unique background images that can be included while satisfying the size limit?

Correct A. 1

B. 0

C. 2

D. 3

Correct Answer: A

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Question 3 View Details

A document contains $45,000$ characters (including spaces). It is to be printed on A4 paper (width $21$ cm, height $29.7$ cm) using Times New Roman 12‑pt font. Each character occupies $0.2$ cm in width. The left and right margins are $2.5$ cm each, and the top and bottom margins are $3$ cm each. Line spacing is 1.5 lines, giving a line height of $0.5$ cm. How many pages are required to print the whole document?

A. 16

B. 10

Correct C. 12

D. 14

Correct Answer: C

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Question 4 View Details

List the sequence of process states for a process that is created, becomes ready, is allocated the CPU, requests I/O, returns to ready after the I/O completes, and finally terminates.

A. New → Running → Ready → Waiting → Ready → Terminated

B. New → Ready → Running → Ready → Waiting → Terminated

C. New → Ready → Waiting → Running → Ready → Terminated

Correct D. New → Ready → Running → Waiting → Ready → Terminated

Correct Answer: D

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Question 5 View Details

Consider a relation R(A,B,C,D) with the functional dependencies $A \rightarrow B$ and $B \rightarrow C$. Determine all candidate keys of R and state the highest normal form (1NF, 2NF, 3NF, BCNF) that R satisfies.

A. Candidate key: AB; Highest normal form: 2NF

B. Candidate key: BD; Highest normal form: 3NF

C. Candidate key: AC; Highest normal form: BCNF

Correct D. Candidate key: AD; Highest normal form: 1NF

Correct Answer: D

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Question 6 View Details

Consider the following pseudocode: ``` x = 0 for i = 1 to 5: for j = 1 to i: if (i*j) \bmod 3 = 0: continue x = x + i - j ``` What is the final value of `x` after the loops finish?

A. 10

Correct B. 14

C. 16

D. 12

Correct Answer: B

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Question 7 View Details

Relation R(E,F,G,H) has the functional dependencies: E$\rightarrow$F, F$\rightarrow$G, G$\rightarrow$H, and GH$\rightarrow$E. Is it possible to decompose R into a set of relations that are all in Boyce‑Codd Normal Form (BCNF), while preserving all functional dependencies and ensuring a lossless‑join? If such a decomposition exists, give one example; if not, explain why.

Correct A. No such decomposition exists; any BCNF decomposition will lose at least one dependency (e.g., GH→E).

B. It is possible to decompose R into BCNF relations such as R1(E,F), R2(F,G), and R3(G,H), which maintains a lossless join.

C. Yes, a BCNF decomposition is possible; for example, decompose into R1(E,F) and R2(F,G,H) which preserves all dependencies.

D. A lossless‑join BCNF decomposition can be achieved by splitting R into R1(E,F,G) and R2(G,H), preserving all functional dependencies.

Correct Answer: A

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Question 8 View Details

An A4‑size report (210 mm × 297 mm) is typed in Times New Roman 12 pt with 1.5 line spacing. The margins are 20 mm on the left and right and 25 mm on the top and bottom. A header occupies 12 mm of height and a footer occupies 10 mm. Assume an average word consists of 5 letters plus a space (6 characters) and that the average character width at 12 pt is 0.2 mm. If the report contains 8 000 words, how many whole pages are required to print the document? (Round up to the next whole page.)

A. 1

B. 3

Correct C. 2

D. 4

Correct Answer: C

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Question 9 View Details

A system encrypts data with AES‑256 in CBC mode using a random 128‑bit IV. An attacker can try $10^{9}$ keys per second. Assuming the key is uniformly random, estimate the expected time (in years) for the attacker to find the correct key by exhaustive search. Give your answer in scientific notation rounded to two significant figures.

Correct A. 1.8×10^60 years

B. 2.5×10^59 years

C. 9.0×10^60 years

D. 1.2×10^61 years

Correct Answer: A

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Question 10 View Details

A population has an unknown mean $\mu$ for a measurement X. The population standard deviation is known to be $\sigma = 9$. A random sample of $n = 25$ observations yields a sample mean $\bar{x}=48$. Test the null hypothesis $H_{0}: \mu = 45$ against the two‑tailed alternative at the 5 % significance level using the appropriate z‑test. Compute the test statistic, the p‑value (to three decimal places), and state the conclusion.

A. z = 0.500, p = 0.617, fail to reject H₀

Correct B. z = 1.667, p = 0.095, fail to reject H₀

C. z = 2.333, p = 0.020, reject H₀

D. z = 1.200, p = 0.230, fail to reject H₀

Correct Answer: B

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Question 11 View Details

Consider the following pseudo‑code: ``` count = 0 for i = 1 to n: for j = i to n: if (i + j) mod 3 = 0: count = count + 1 output count ``` If $n = 10$, what number is displayed?

A. 20

Correct B. 18

C. 22

D. 15

Correct Answer: B

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Question 12 View Details

A computer uses an 8‑bit signed two's‑complement representation. What decimal integer does the binary pattern $11010110$ represent?

A. -46

Correct B. -42

C. 42

D. -38

Correct Answer: B

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Question 13 View Details

A company has been allocated the network 192.168.48.0/22. It must create sub‑networks for three departments that need at least 200, 50 and 20 usable host addresses respectively. Using VLSM, assign the smallest possible subnet mask to each department and give the first usable IP address of the department that requires 50 hosts.

A. 255.255.255.240, 192.168.49.5

Correct B. 255.255.255.192, 192.168.49.1

C. 255.255.255.224, 192.168.48.1

D. 255.255.255.128, 192.168.49.1

Correct Answer: B

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Question 14 View Details

A presenter has prepared 20 slides. The first 5 slides each take 45 seconds, the next 10 slides each take 30 seconds, and the remaining slides each take 1 minute. After slide 12 a 2‑minute question‑and‑answer session is held. What is the total presentation time expressed in minutes and seconds?

A. 13 minutes 45 seconds

Correct B. 15 minutes 45 seconds

C. 16 minutes 45 seconds

D. 15 minutes 30 seconds

Correct Answer: B

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Question 15 View Details

A file of size $3.5$ GB is to be copied onto a USB flash drive that has a total capacity of $8$ GB and already contains $2.1$ GB of data. After the copy, what percentage of the drive's total capacity will be used? Express your answer as a whole number percentage.

A. 26

B. 59

Correct C. 70

D. 44

Correct Answer: C

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Question 16 View Details

A company has been allocated the address block $10.0.0.0/22$. It needs to create subnets for three divisions requiring at least 50, 20, and 10 usable host addresses respectively, using VLSM and allocating the largest subnet first. What subnet mask (in dotted‑decimal notation) should be assigned to the division needing 50 hosts, and how many usable host addresses remain unassigned after all three subnets are allocated?

A. 255.255.255.192, 912

B. 255.255.255.240, 904

Correct C. 255.255.255.192, 916

D. 255.255.255.224, 916

Correct Answer: C

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Question 17 View Details

A web page of size $2.5\text{ MB}$ is requested over a TCP connection with a round‑trip time (RTT) of $80\text{ ms}$. The connection starts with an initial congestion window of $10$ MSS, where the maximum‑segment‑size (MSS) is $1460$ bytes. The slow‑start phase continues until the congestion window reaches the slow‑start threshold of $64$ MSS, after which the window grows linearly by $1$ MSS per RTT. Assuming no packet loss, how many RTTs are required to transmit the entire page?

A. 30

Correct B. 27

C. 28

D. 26

Correct Answer: B

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Question 18 View Details

A server uses a RAID 5 array consisting of four identical disks, each of capacity $2\text{ TB}$. Each disk can sustain a sequential write speed of $150\text{ MB/s}$. For RAID 5, a write operation incurs a write penalty of four disk I/O operations. The system must support a sustained write workload of $200\text{ MB/s}$. Determine whether the existing RAID 5 array can meet this requirement. If it cannot, calculate the minimum number of additional identical disks that must be added (keeping the RAID 5 configuration) to achieve the required write throughput.

Correct A. 2

B. 4

C. 3

D. 1

Correct Answer: A

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Question 19 View Details

The authoritative name server for the domain $example.com$ holds a CNAME record that maps $example.com$ to $www.example.com$ with a TTL of $43200$ seconds, and an A record for $www.example.com$ with IP address $203.0.113.5$ and a TTL of $86400$ seconds. A recursive resolver cached both records at exactly 12:00 PM. At 3:30 PM the resolver receives another query for $example.com$. Assuming no other caching events, what IP address will be returned, and what are the remaining TTL values (in seconds) for the A record and the CNAME record at that moment?

A. 203.0.113.5, 72000, 30600

B. 203.0.113.5, 73800, 36000

Correct C. 203.0.113.5, 73800, 30600

D. 203.0.113.5, 72000, 32400

Correct Answer: C

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Question 20 View Details

An organization has been assigned the IPv6 prefix $2001:0db8:85a3::/48$. It must allocate subnets to five departments, each requiring at least $2^{20}$ IPv6 addresses. Using the smallest possible subnet size that satisfies each department, (a) what prefix length should be assigned to each department, and (b) how many such subnets remain unallocated from the original /48 after assigning subnets to all five departments?

A. /104, 2^55 - 5

Correct B. /104, 2^56 - 5

C. /104, 2^56 - 4

D. /108, 2^56 - 5

Correct Answer: B

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Question 21 View Details

An $8$-inch by $11$-inch page has $2$-inch margins on all sides. The document uses Times New Roman $12$-pt font with a character width of $0.12$ in and line spacing of $1.5$. If a report contains $2{,}500$ words, assuming an average word length of 5 letters plus one space ($6$ characters per word), how many whole pages are required to print the report? (Round up to the next whole page.)

Correct A. 15

B. 13

C. 14

D. 16

Correct Answer: A

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Question 22 View Details

In a spreadsheet, cell A1 contains the sales figure for year 1, which is $\text{₦}150{,}000$. For each subsequent year (cells A2 to A5), the sales grow by a rate that depends on the previous year's sales: if the previous year's sales exceed $\text{₦}200{,}000$, the growth rate is $8\%$; otherwise it is $12\%$. Using this rule, what is the sales figure for year 5 (cell A5)? Give your answer rounded to the nearest naira.

A. 219000

Correct B. 227598

C. 236029

D. 204263

Correct Answer: B

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Question 23 View Details

The following pseudo‑code is executed with the integer variable n = 10: ``` 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 output count ``` What number is displayed when the program finishes?

A. 21

B. 24

C. 15

Correct D. 18

Correct Answer: D

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Question 24 View Details

A network uses the address block 192.168.48.0/22. Three departments need subnets with the following minimum host requirements: Department A - 50 hosts, Department B - 20 hosts, Department C - 10 hosts. Subnets must be allocated using the smallest possible masks to minimise waste. What is the broadcast address of the subnet assigned to Department B?

A. 192.168.48.111

Correct B. 192.168.48.95

C. 192.168.48.127

D. 192.168.48.63

Correct Answer: B

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Question 25 View Details

A password policy requires passwords to be exactly 8 characters long. The allowed character set consists of 26 uppercase letters, 26 lowercase letters, 10 digits, and the six symbols @, #, $, %, &, *. A valid password must contain at least one uppercase letter, at least one digit, and may contain at most two of the special symbols. How many different passwords satisfy the policy? Give the exact integer count.

A. 314025254033921

B. 312000000000000

Correct C. 314025254033920

D. 315000000000000

Correct Answer: C

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