Practice gce model questions vol1 computer_studies 2017 Past Questions

Question 1 View Details

A company has been allocated the Class B network \(172.16.0.0\). They need to create subnets for three departments—Sales, Development and HR—each requiring at least \(200\) hosts. Subnets must use contiguous block sizes (a power of two). The network uses a hierarchical design where each department's subnet connects to a central router, and the router has a maximum of six interfaces (including the backbone). Determine the subnet mask that should be assigned to each department and calculate how many host addresses remain unused in the original Class B address space after allocating the three subnets.

Correct A. Subnet mask: 255.255.255.0 (/24); Unused addresses: 64768

B. Subnet mask: 255.255.254.0 (/23); Unused addresses: 64000

C. Subnet mask: 255.255.255.128 (/25); Unused addresses: 65152

D. Subnet mask: 255.255.252.0 (/22); Unused addresses: 62464

Correct Answer: A

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Question 2 View Details

A \(12\text{ MB}\) file is first compressed using a loss‑less algorithm that reduces its size by \(35\%\). The compressed file is then encrypted with a block cipher that adds a \(16\text{‑byte}\) header to each \(4\text{ KB}\) block. The file system stores data in blocks of \(4\text{ KB}\). Calculate (a) the total number of disk blocks required to store the encrypted file, and (b) the total amount of wasted space (in bytes) due to block padding.

A. 2000 blocks; Wasted space: 1600 bytes

B. 1998 blocks; Wasted space: 1024 bytes

Correct C. 2005 blocks; Wasted space: 1635 bytes

D. 2010 blocks; Wasted space: 2048 bytes

Correct Answer: C

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Question 3 View Details

What is the name of the battery‑powered memory that retains the BIOS configuration settings when the computer is turned off?

A. EPROM (battery‑powered memory)

Correct B. CMOS (battery‑powered memory)

C. RAM (battery‑powered memory)

D. Flash (battery‑powered memory)

Correct Answer: B

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Question 4 View Details

In a LAN operating at \(100\text{ Mbps}\), the maximum Ethernet frame size is \(1500\text{ bytes}\). In a star topology the central hub introduces a processing delay of \(2\,\mu\text{s}\) per frame, and the signal must travel \(5\,\mu\text{s}\) from the source to the hub and another \(5\,\mu\text{s}\) from the hub to the destination (propagation delay). In a bus topology there is no hub delay and the signal travels only \(5\,\mu\text{s}\) from source to destination. Assuming negligible other delays, compute the total time from the start of transmission to the end of reception for (a) the star topology and (b) the bus topology, and state the difference between the two times.

A. Star: 134 µs; Bus: 126 µs; Difference: 8 µs

B. Star: 130 µs; Bus: 124 µs; Difference: 6 µs

Correct C. Star: 132 µs; Bus: 125 µs; Difference: 7 µs

D. Star: 135 µs; Bus: 125 µs; Difference: 10 µs

Correct Answer: C

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Question 5 View Details

Consider a relation R(A,B,C,D,E) with the functional dependencies: A → B, BC → D, and D → E. (a) List all candidate keys of R. (b) Decompose R into BCNF relations. (c) If the original relation contains 1200 tuples, what is the maximum possible total number of tuples stored across all the BCNF tables after decomposition, assuming the decomposition is lossless‑join and introduces no unnecessary duplicate tuples beyond those required for the join?

A. Candidate key: AD; BCNF tables: R1(A,B), R2(B,C), R3(D,E); Maximum total tuples: 2400

Correct B. Candidate key: AC; BCNF tables: R1(A,B), R3(D,E), R4(A,C,D); Maximum total tuples: 3600

C. Candidate key: AB; BCNF tables: R1(A,B), R3(D,E), R4(A,B,D); Maximum total tuples: 4800

D. Candidate key: AC; BCNF tables: R1(A,B), R2(B,C), R4(A,C,D); Maximum total tuples: 3000

Correct Answer: B

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Question 6 View Details

The HTML page contains a <div> element with class "container" inside a parent <div> with id "main". The element also has the additional class "special". The following CSS rules apply: 1. #main .container { width: \(300\)px; padding: \(10\)px; } 2. .container { width: \(280\)px; box-sizing: border-box; } 3. .container.special { width: \(260\)px; } The element has a border of \(2\)px on each side and a margin of \(5\)px on each side. Assuming the box‑model uses the declared box‑sizing, what is the total horizontal space (margin + border + padding + content) occupied by the element, in pixels?

A. 270

Correct B. 310

C. 330

D. 294

Correct Answer: B

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Question 7 View Details

Within a class of \(20\) students, the sum of all Mathematics marks (out of 100) is \(1500\) and the sum of all English marks (out of 100) is \(1300\). Mathematics carries a credit weight of \(3\) and English a weight of \(2\). The current weighted average of the class is therefore calculated using these weights. The school wishes to raise the class weighted average to at least \(75\). A particular student, who currently has \(45\) in Mathematics and \(50\) in English, will sit a supplementary exam for both subjects and is expected to obtain the same mark in each subject. What is the minimum mark the student must obtain in each subject to achieve the target class average?

A. 85

Correct B. 80

C. 70

D. 100

Correct Answer: B

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Question 8 View Details

Consider the following pseudo‑code that processes an array \(A[1\ldots n]\) of integers, where \(n\) is even: ``` count = 0 for i = 1 to n: if A[i] is even: for j = i+1 to n: count = count + 1 ``` Assume exactly half of the elements are even and they occupy the first \(n/2\) positions of the array (i.e., \(A[1]\) to \(A[n/2]\) are even). Express, as a simplified function of \(n\), the total number of times the statement `count = count + 1` is executed. Then state the algorithm's time‑complexity using Big‑O notation.

A. (\frac{3n^{2}}{8} + \frac{n}{4}), O(n^{2})

Correct B. (\frac{3n^{2}}{8} - \frac{n}{4}), O(n^{2})

C. (\frac{3n^{2}}{8} - \frac{n}{2}), O(n\log n)

D. (\frac{n^{2}}{2} - \frac{n}{2}), O(n^{2})

Correct Answer: B

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Question 9 View Details

Three security threats have been identified with the following likelihood (L) and impact (I) scores (on a scale of 1-5): - Threat A: L = 4, I = 5 - Threat B: L = 3, I = 4 - Threat C: L = 5, I = 3 The risk score for each threat is calculated as \(R = L \times I\). For each threat a control can be implemented that reduces its likelihood as shown, at the indicated cost: - Control A reduces L to 2, cost = ₦30,000 - Control B reduces L to 1, cost = ₦20,000 - Control C reduces L to 3, cost = ₦15,000 For each control compute the reduction in risk per ₦10,000 spent. Which control(s) give the greatest reduction per ₦10,000?

A. Control A and Control C

B. Control A and Control B

C. Control A only

Correct D. Control B and Control C

Correct Answer: D

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Question 10 View Details

Place the following milestones in the correct chronological order, from earliest to latest, using the letters provided: a) Invention of the transistor b) Release of the first IBM PC c) Development of ENIAC d) Introduction of the World Wide Web Provide your answer as a comma‑separated list of the letters.

A. a, c, b, d

B. c, a, d, b

C. c, b, a, d

Correct D. c, a, b, d

Correct Answer: D

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Question 11 View Details

Computer A was introduced 2 years before Computer B. Computer B was released in the same year that Computer C was announced. If Computer C was announced in \(1975\), in which year was Computer A released?

Correct A. 1973

B. 1974

C. 1975

D. 1972

Correct Answer: A

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Question 12 View Details

The first commercially successful microprocessor was released in \(1971\) and the first widely recognised personal computer was released in \(1975\). Let \(X\) be the sum of these two years. If \(X\) is divided by \(2\) to give \(Y\), what is the value of \(Y\)?

A. 1972

B. 1975

Correct C. 1973

D. 1974

Correct Answer: C

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Question 13 View Details

A text file contains \(1500\) characters, each stored using \(8\) bits. The file is first compressed, reducing the total number of bits by \(20\%\). The compressed file is then encoded using Manchester encoding, which doubles the number of bits. What is the final number of bits required to store the file?

A. 12000

B. 24000

Correct C. 19200

D. 9600

Correct Answer: C

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Question 14 View Details

An IPv4 network uses the address \(192.168.12.0\) with subnet mask \(255.255.255.240\). How many usable host addresses are available in this subnet?

A. 13

B. 15

C. 16

Correct D. 14

Correct Answer: D

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Question 15 View Details

Class A has \(20\) students with an average score of \(68\). Class B has \(30\) students with an average score of \(74\). The lowest‑scoring student in Class B, who scored \(55\), transfers to Class A. What is the new average score of Class A (rounded to two decimal places)?

A. 64.76

Correct B. 67.38

C. 64.32

D. 70.75

Correct Answer: B

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Question 16 View Details

A company estimates the probability of a security breach in a year as \(12\%\). It installs three security measures sequentially: a firewall that reduces the breach probability by \(30\%\), encryption that reduces the remaining probability by \(40\%\), and employee training that reduces the remaining probability by \(25\%\). What is the final probability (as a percentage, to two decimal places) that a breach will occur after all three measures are in place?

A. 5.67\%

Correct B. 3.78\%

C. 2.95\%

D. 4.12\%

Correct Answer: B

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Question 17 View Details

Consider the following Python program:\n\n```python\ndef f(k):\n total = 0\n for i in range(1, k+1):\n if i % 2 == 0:\n total += i // 2\n else:\n total += 3 * i + 1\n return total\n\nn = 10\nresult = f(n) + f(n-1)\nprint(result)\n```\nWhat integer value is printed when the program is executed?

A. 175

Correct B. 185

C. 195

D. 180

Correct Answer: B

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Question 18 View Details

The ENIAC computer was completed in \(1945\). The Intel 4004 microprocessor, the first commercially successful microprocessor, was released in \(1971\). How many years later was the microprocessor introduced?

A. 30

B. 28

C. 24

Correct D. 26

Correct Answer: D

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Question 19 View Details

A computer has a processor that runs at \(2.4\) GHz and a data bus that is \(64\) bits wide. Assuming the bus can transfer one word per clock cycle and there are no bottlenecks, what is the maximum data transfer rate in gigabytes per second (GB/s)? Give your answer to one decimal place.

A. 21.6

Correct B. 19.2

C. 18.4

D. 20.0

Correct Answer: B

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Question 20 View Details

In a spreadsheet, column A contains product codes, column B the unit price (in naira), and column C the quantity sold. A discount of \(10\%\) is applied to the total sales of a product if the quantity sold exceeds 100 units; otherwise no discount is given.\n\n(a) Write a single formula that could be placed in cell D2 to calculate the net revenue for that row, using the IF function and appropriate arithmetic.\n(b) Using your formula, calculate the net revenue for a product with code "P102" where the unit price is \(\text{₦}250\) and the quantity sold is 120 units.

A. Formula: =IF(C2>100,B2*(C2-10),B2*C2); Result: 27500

B. Formula: =IF(C2>100,B2*C2,B2*C2*0.9); Result: 30000

Correct C. Formula: =IF(C2>100,B2*C2*0.9,B2*C2); Result: 27000

D. Formula: =IF(C2>100,B2*C2*0.85,B2*C2); Result: 25500

Correct Answer: C

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Question 21 View Details

A software company is testing three modules. Module A has 2000 lines of code (LOC) and a defect density of 0.8 defects per 100 LOC. The testing process finds \(90\%\) of its defects. Module B has 1500 LOC and a defect density of 1.2 defects per 100 LOC, with a detection rate of \(75\%\). Module C has 2500 LOC, a defect density of 0.6 defects per 100 LOC, and a detection rate of \(85\%\). Assuming defects are independent, what is the expected total number of defects that remain undetected after testing, expressed to two decimal places?

A. 6.45

B. 9.12

C. 7.20

Correct D. 8.35

Correct Answer: D

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Question 22 View Details

Two sorting algorithms, A and B, were timed on the same computer for three input sizes. The recorded execution times (in milliseconds) are:\n\n| n | Algorithm A | Algorithm B |\n|---|-------------|-------------|\n| 1000 | 12 | 15 |\n| 2000 | 48 | 30 |\n| 4000 | 192 | 60 |\n\nWhen the input size is doubled, the time for Algorithm A multiplies by a factor of 4, while the time for Algorithm B multiplies by a factor of 2. Based on this evidence, which algorithm has the lower asymptotic time‑complexity for large inputs? Answer with the letter of the algorithm (A or B).

A. A

B. D

Correct C. B

D. C

Correct Answer: C

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Question 23 View Details

Consider the following Python program:\n\n```python\ncount = 0\nfor i in range(1, 5): # i = 1,2,3,4\n for j in range(i, 6): # j starts at i up to 5\n if i + j == 6:\n continue\n if i * j > 12:\n break\n count += 1\nprint(count)\n```\n\nWhat integer value is printed when the program is executed?

A. 9

B. 7

Correct C. 8

D. 12

Correct Answer: C

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Question 24 View Details

A `<div>` element is placed inside a container that is exactly 800\,px wide. The CSS for the `<div>` is:\n\n```css\ndiv {\n width: 80%; /* percentage of the container width */\n padding: 5%; /* percentage of the container width */\n border: 2px solid black;\n margin: 10px;\n box-sizing: border-box;\n}\n```\n\nInside the `<div>` there is an `<img>` whose width is set to `100%` of the `<div>`'s content width. What is the rendered width of the image in pixels? Give your answer as an integer number of pixels.

A. 560

Correct B. 556

C. 572

D. 620

Correct Answer: B

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Question 25 View Details

In a spreadsheet, cells A1 through A5 contain the numbers 12, 15, 9, 20 and 8 respectively. The following formulas are entered:\n\n- B1: `=IF(AVERAGE(A1:A5)>14, "High", "Low")`\n- B2: `=COUNTIF(A1:A5,">=15")*MIN(A1:A5)`\n- B3: `=SUMPRODUCT((A1:A5>10)*(A1:A5<18),A1:A5)`\n\nWhat values are displayed in cells B1, B2 and B3 after the formulas are evaluated? List the three results in order, separated by commas.

A. Low, 15, 27

B. High, 16, 27

C. Low, 16, 30

Correct D. Low, 16, 27

Correct Answer: D

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