Practice gce model questions vol1 computer_studies 2020 Past Questions

Question 1 View Details

Consider a network of 8 computers. In the current star topology, each link between a computer and the central hub introduces a transmission delay of 2 ms and the hub adds a processing delay of 0.5 ms for each message it forwards. To broadcast a message from one computer to all the others, the originating computer first sends the message to the hub, after which the hub forwards it sequentially to each of the remaining 7 computers, one at a time. In an alternative full mesh topology, each pair of computers is directly connected; each direct link has a transmission delay of 1 ms and each computer's network interface adds a processing delay of 0.2 ms per transmitted message. Assume that in the mesh a computer can send the broadcast to all others simultaneously over the separate links. Calculate the percentage reduction in total broadcast time when switching from the star to the mesh topology. Give your answer to two decimal places.

A. 102.00%

Correct B. 93.00%

C. 95.20%

D. 88.75%

Correct Answer: B

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Question 2 View Details

Two sorting algorithms are being compared. Algorithm A has a running time of $T_A = n^{2}$ microseconds for an input of size $n$. Algorithm B runs in $T_B = 100\,n\log_{2} n$ microseconds. Determine the smallest integer value of $n$ for which Algorithm B is faster than Algorithm A. Give your answer as an integer.

A. 1000

Correct B. 996

C. 1024

D. 995

Correct Answer: B

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Question 3 View Details

An older computer system uses a 16‑bit address bus and a word size of 4 bytes. (i) How many distinct memory locations can be addressed? (ii) What is the maximum amount of memory, in kilobytes, that can be directly addressed by this system? Give your answer to two decimal places.

A. 64,512 locations; 255.00 KB

Correct B. 65,536 locations; 256.00 KB

C. 65,000 locations; 250.00 KB

D. 66,000 locations; 260.00 KB

Correct Answer: B

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Question 4 View Details

A desktop computer consists of a CPU that consumes 65 W, a monitor that consumes 40 W, and a hard‑disk that consumes 10 W. The power‑supply unit (PSU) is rated at 500 W and operates at an efficiency of 70 %. (i) What is the total power drawn from the mains when the computer is running? (ii) How much of that power is dissipated as heat by the PSU? (iii) If the computer runs for 5 hours, what is the energy consumption in kilowatt‑hours and the cost, assuming electricity costs ₦25 per kWh? Give the cost to two decimal places.

A. 165.00 W; 50.00 W; ₦21.00

Correct B. 164.29 W; 49.29 W; ₦20.54

C. 160.00 W; 45.00 W; ₦19.00

D. 170.00 W; 55.00 W; ₦22.50

Correct Answer: B

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Question 5 View Details

Consider a relation R(A, B, C, D) with the following functional dependencies: 1. A → B 2. BC → D 3. D → A (a) List all candidate keys of R. (b) State the highest normal form (1NF, 2NF, 3NF, BCNF) that R currently satisfies. (c) Decompose R into a collection of relations that are in BCNF. Show the resulting relations and their attributes.

A. Candidate keys: ABC, ABD, ACD; Highest NF: BCNF; BCNF decomposition: R1(A,B), R2(B,D), R3(C,D)

B. Candidate keys: B, C, D; Highest NF: 1NF; BCNF decomposition: R1(A,B,C), R2(D)

C. Candidate keys: AB, AD, BD; Highest NF: 2NF; BCNF decomposition: R1(A,B), R2(B,C), R3(C,D)

Correct D. Candidate keys: BC, CD, AC; Highest NF: 3NF; BCNF decomposition: R1(A,B), R3(D,A), R4(D,C)

Correct Answer: D

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Question 6 View Details

An office has 5 desktop computers, each drawing an average of $120\text{ W}$. A network switch uses $30\text{ W}$ and a printer uses $80\text{ W}$. They need a UPS that can run the whole load for 20 minutes. The UPS operates at $90\%$ efficiency and has a power factor of $0.8$. The UPS battery is a 12 V unit. Determine the minimum UPS rating in volt‑amps (VA) and the minimum battery capacity in amp‑hours (Ah) required (round each up to the nearest whole number).

A. 1000 VA and 25 Ah

B. 950 VA and 21 Ah

Correct C. 987 VA and 22 Ah

D. 900 VA and 20 Ah

Correct Answer: C

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Question 7 View Details

Consider the following pseudo‑code:\n\n``` count ← 0 for i ← 1 to n do for j ← i to n do if (j mod i = 0) then count ← count + 1 end if end for end for ```\n\nIf $n = 12$, what is the final value of `count` after the loops finish?

A. 34

B. 30

Correct C. 35

D. 36

Correct Answer: C

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Question 8 View Details

An office floor is a rectangle $30\text{ m}$ long and $20\text{ m}$ wide. Twenty computers are to be networked. Three possible topologies are considered:\n\n* Star: a hub is placed at the centre of the rectangle; each computer is connected directly to the hub by a straight cable.\n* Bus: a single backbone cable runs along the longer side (30 m) of the rectangle; each computer taps onto this backbone.\n* Ring: a cable follows the perimeter of the rectangle, connecting the computers placed equally around the edges (including the four corners).\n\nThe cost of cable is $\$0.50$ per metre. Assuming the computers are positioned as described, calculate the total cable cost for each topology and state which topology is cheapest.

A. Bus - $20; Ring - $55; Star - $140.00; cheapest is Bus

B. Bus - $12; Ring - $50; Star - $150.00; cheapest is Bus

Correct C. Bus - $15; Ring - $50; Star - $146.43; cheapest is Bus

D. Bus - $15; Ring - $45; Star - $146.43; cheapest is Ring

Correct Answer: C

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Question 9 View Details

Each day a company generates $2.5\text{ GB}$ of log data. The logs are first compressed, reducing their size by $40\%$. After compression, a parity block equal to $5\%$ of the compressed size is added for error detection. The archived data are stored on DVDs, each holding $4.7\text{ GB}$. How many DVDs are required to store the logs for a 30‑day month?

Correct A. 11 DVDs

B. 10 DVDs

C. 13 DVDs

D. 12 DVDs

Correct Answer: A

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Question 10 View Details

Given the following HTML fragment:\n\n```html\n<div id="main" class="content">\n <p class="text" style="color: orange;">Sample text</p>\n</div>\n```\n\nand the external stylesheet contains these rules (in the order shown):\n\n```css\np { color: black; }\n.content p { color: purple; }\n#main .text { color: teal !important; }\n.text { color: brown; }\np.text { color: pink !important; }\n```\n\nWhat is the final computed colour of the paragraph text when the page is rendered?

Correct A. teal

B. pink

C. brown

D. purple

Correct Answer: A

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Question 11 View Details

In a spreadsheet, cells A1 through A5 contain the numbers 12, 15, 9, 20 and 8 respectively. Cell B1 has the formula =IF(A1>10, A1*0.9, A1*1.1) and this formula is copied down to B5. Cell C1 contains the formula =SUM($B$1:B1) and is copied down to C5. What value is displayed in cell C5 after the copying is complete?

Correct A. 61

B. 55

C. 59

D. 68

Correct Answer: A

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Question 12 View Details

Consider the following CSS rules applied to a <div class="box"> element: ```css .box { width: 200px; padding: 10px 20px; border: 5px solid #000; margin: 15px; box-sizing: content-box; } .box { box-sizing: border-box; } ``` Assuming the second rule overrides the first due to cascade, what is the total horizontal space (including left and right margins) occupied by the element on the page?

A. 210

B. 250

C. 240

Correct D. 230

Correct Answer: D

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Question 13 View Details

Among the following computers, which was introduced earliest? ENIAC, UNIVAC I, IBM 360, Apple II.

A. UNIVAC I

B. IBM 360

C. Apple II

Correct D. ENIAC

Correct Answer: D

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Question 14 View Details

A spreadsheet contains two tables. Table 1 (columns A and B): | A | B | |-----|-----| | P01 | 100 | | P02 | 150 | | P03 | 120 | | P04 | 80 | Table 2 (columns D and E): | D | E | |-----|-----| | P03 | 10% | | P01 | 5% | | P04 | 20% | | P02 | 15% | In cell F2 the formula `=B2*(1‑VLOOKUP(A2,$D$2:$E$5,2,FALSE)/100)` is entered and copied down to F5. Afterwards the user sorts Table 1 by the values in column B in descending order, leaving Table 2 unchanged. What value is displayed in cell F4 after the sorting operation?

Correct A. 95

B. 110

C. 100

D. 85

Correct Answer: A

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Question 15 View Details

A company of 200 employees enforces a password policy that requires a minimum of 8 characters, at least one uppercase letter, one digit and one special character. An audit finds that 30 % of the employees use passwords that satisfy the length requirement but lack a special character, while 10 % use passwords that meet all the stated criteria. The remaining employees use passwords that fail the length requirement. The company plans to add an additional requirement of at least two digits, while assuming the same distribution of compliance for the other criteria. To reduce the proportion of weak passwords (those failing any criterion) to below 15 %, what is the minimum number of employees who must change their passwords to satisfy the new policy?

A. 160

Correct B. 150

C. 130

D. 120

Correct Answer: B

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Question 16 View Details

A survey of five schools records the number of computers and the average weekly usage per computer (in hours) as follows: - School A: 120 computers, 4.5 h - School B: 80 computers, 5.2 h - School C: 150 computers, 3.8 h - School D: 60 computers, 6.0 h - School E: 90 computers, 4.0 h Calculate the overall average weekly usage per computer across all schools. Then state whether this overall average exceeds the target of 4.8 hours, and if it does, give the percentage excess rounded to one decimal place. If it does not exceed, give the percentage shortfall rounded to one decimal place.

A. Overall average = 4.55 h; it is 5.2% below the target.

B. Overall average = 4.49 h; it is 6.4% above the target.

C. Overall average = 4.60 h; it is 3.1% above the target.

Correct D. Overall average = 4.49 h; it is 6.4% below the target.

Correct Answer: D

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Question 17 View Details

Consider the following HTML element and CSS rules. HTML: <p id="intro" class="highlight">Sample text</p> CSS rules (in the order shown): 1) p { color: black; } 2) .highlight { color: blue; } 3) #intro { color: green; } 4) div p { color: red; } 5) p.highlight { color: orange; } Using the CSS cascade and specificity rules, determine the final colour of the text inside the paragraph element. Provide the colour name.

A. red

B. blue

Correct C. green

D. orange

Correct Answer: C

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Question 18 View Details

A 2 MB file is compressed in two successive stages. Stage 1: Run‑length encoding reduces the file size by 30 % of the original size. Stage 2: Huffman coding then reduces the remaining size by an amount equal to 40 % of the original size. Calculate (a) the final size of the file after both stages (to two decimal places) and (b) the overall compression ratio expressed as a percentage of the original size.

A. 0.54 MB and 27 %

B. 0.66 MB and 33 %

C. 0.70 MB and 35 %

Correct D. 0.60 MB and 30 %

Correct Answer: D

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Question 19 View Details

A company must connect 12 computers to a central server. Two possible network topologies are considered. Star topology: each computer is linked directly to a hub placed at the server. The cable lengths (in metres) from the hub to the computers are: 5, 7, 6, 8, 5, 9, 7, 6, 8, 5, 7, 6. Bus topology: the computers are arranged in a straight line with an equal spacing of 2 m between adjacent computers, and a single bus cable runs the length of the line, connecting the first and the last computer. Calculate the total cable length required for each topology and state which topology uses less cable, giving the difference in metres (rounded to the nearest metre).

A. Bus topology uses less cable by 45 m

B. Star topology uses less cable by 30 m

C. Star topology uses less cable by 12 m

Correct D. Bus topology uses less cable by 57 m

Correct Answer: D

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Question 20 View Details

A loan of $500{,}000$ Naira is to be repaid over 5 years with interest charged at 8 % per annum (nominal) and payable monthly. (a) Using the standard loan amortisation formula, calculate the monthly repayment amount (rounded to the nearest Naira). (b) After the first 12 repayments have been made, determine the outstanding balance (rounded to the nearest Naira).

A. Monthly payment = 9 900 Naira; balance after 12 months = 420 500 Naira

Correct B. Monthly payment = 10 154 Naira; balance after 12 months = 415 083 Naira

C. Monthly payment = 10 500 Naira; balance after 12 months = 410 000 Naira

D. Monthly payment = 9 850 Naira; balance after 12 months = 418 200 Naira

Correct Answer: B

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Question 21 View Details

The first commercially successful microprocessor was released in 1971 and the first personal computer with a graphical user interface was released in 1984. How many years later was the GUI personal computer released?

A. 14

Correct B. 13

C. 15

D. 12

Correct Answer: B

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Question 22 View Details

A company requires passwords of length 8 that may use uppercase letters (26), lowercase letters (26) and digits (10). Each password must contain at least one digit. How many possible passwords satisfy the policy, and what is the probability that a random password guess meets the policy and is correct on the first try?

A. Number of passwords = 62^8 - 52^8; probability = 1\/(62^8)

Correct B. Number of passwords = 62^8 - 52^8; probability = 1/(62^8 - 52^8)

C. Number of passwords = 62^8 - 52^7; probability = 1\/(62^8 - 52^7)

D. Number of passwords = 62^8 - 36^8; probability = 1\/(62^8 - 36^8)

Correct Answer: B

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Question 23 View Details

A spreadsheet records sales data for five products as follows:\n\nProduct 1: Units sold = 120, Unit price = $\£15$, Category = A\nProduct 2: Units sold = 80, Unit price = $\£20$, Category = A\nProduct 3: Units sold = 50, Unit price = $\£30$, Category = B\nProduct 4: Units sold = 90, Unit price = $\£25$, Category = B\nProduct 5: Units sold = 60, Unit price = $\£10$, Category = A\n\nThe company gives a 5% discount on the total sales of Category A items only if the total units sold of Category A exceed 200. After any discount, a flat tax of 12% is applied to the subtotal. Calculate the final amount payable (in pounds).

A. 8300

Correct B. 8456

C. 8500

D. 8420

Correct Answer: B

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Question 24 View Details

Write a Python function that receives a list of integers and returns the length of the longest contiguous sub‑list whose sum is a prime number. Using the list $[4, 6, 7, 2, 5, 3]$, what length does the function return?

A. 3

B. 6

Correct C. 5

D. 4

Correct Answer: C

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Question 25 View Details

A survey of 160 computer users gives the following frequency distribution of ages:\n\n15‑24 years: 40 users\n25‑34 years: 55 users\n35‑44 years: 30 users\n45‑54 years: 20 users\n55‑64 years: 15 users\n\n(a) Estimate the inter‑quartile range (IQR) of the ages (to one decimal place).\n(b) What percentage of users are older than 40 years? (Give your answer to one decimal place.)

A. IQR ≈ 16.0 years; percentage >40 ≈ 31.2%

B. IQR ≈ 20.3 years; percentage >40 ≈ 27.5%

Correct C. IQR ≈ 18.5 years; percentage >40 ≈ 29.4%

D. IQR ≈ 18.5 years; percentage >40 ≈ 35.0%

Correct Answer: C

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