Practice neco computer_studies 2022 Past Questions

Question 1 View Details

Given the following HTML and CSS, determine the background colour that will be displayed for the paragraph element with id "para" in a standards‑compliant browser. HTML: ```html <div id="outer" class="box"> <div class="inner highlight"> <p id="para">Sample text</p> </div> </div> ``` CSS: ```css .box { background-color: yellow; } .inner { background-color: green; } .highlight { background-color: blue; } #para { background-color: red; } div { background-color: orange; } .box .inner { background-color: purple; } #outer .highlight { background-color: pink; } ```

A. green

B. purple

C. pink

Correct D. red

Correct Answer: D

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Question 2 View Details

A container has a fixed width of 1200 px. Inside it a CSS grid is defined with the rule ```css grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); column-gap: 20px; ``` What is the maximum number of columns that can be placed in the grid without causing overflow?

A. 5

B. 6

Correct C. 4

D. 3

Correct Answer: C

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Question 3 View Details

A sales spreadsheet contains the following data for four regions: | Region | Sales (₦) | |--------|-----------| | North | 120,000 | | South | 80,000 | | East | 150,000 | | West | 60,000 | Commission is calculated with the rule: if sales exceed 100,000 ₦ the commission rate is 5 %; otherwise the rate is 3 %. The commission for each region is Sales × Rate. What is the total commission payable for all regions combined (in Naira)?

A. 16500

B. 18000

Correct C. 17700

D. 20500

Correct Answer: C

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Question 4 View Details

Consider the following pseudo‑code: ``` total = 0 for i = 1 to n for j = i to n if (i + j) mod 3 = 0 total = total + 1 end if end for end for ``` What is the worst‑case time complexity of this algorithm, expressed in Big‑O notation as a function of n?

Correct A. O(n^2)

B. O(n^3)

C. O(n log n)

D. O(n)

Correct Answer: A

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Question 5 View Details

A company owns the network 192.168.0.0/24 and must create subnets for four departments that need 50, 30, 20 and 10 usable host addresses respectively. Using VLSM and allocating the largest subnet first, what is the network address assigned to the third department (the one requiring 20 hosts)?

Correct A. 192.168.0.96

B. 192.168.0.128

C. 192.168.0.64

D. 192.168.0.80

Correct Answer: A

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Question 6 View Details

A program contains the following nested loops: for i = 1 to \(n\)\n for j = 1 to i\n if j mod 3 = 0 then\n count = count + 1\nEnd For\nIf \(n = 12\) and each execution of the statement \(count = count + 1\) takes \(0.5\) milliseconds, what is the total execution time in milliseconds?

A. 14

Correct B. 11

C. 10

D. 12

Correct Answer: B

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Question 7 View Details

A school network is allocated the class‑B address block \(172.16.0.0/16\). Each subnet must support at least 200 usable host addresses. Using variable‑length subnet masking (VLSM), determine (i) the maximum number of subnets that can be created and (ii) the subnet mask (in dotted‑decimal notation) for each subnet.

A. 128 subnets, each with mask 255.255.254.0 (\/23)

B. 64 subnets, each with mask 255.255.252.0 (\/22)

Correct C. 256 subnets, each with mask 255.255.255.0 (/24)

D. 512 subnets, each with mask 255.255.255.128 (\/25)

Correct Answer: C

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Question 8 View Details

Consider the Python function below: ```python def digit_sum_multiples(n): total = 0 for k in range(1, n+1): if k % 4 == 0 and k % 6 != 0: # add sum of decimal digits of k while k > 0: total += k % 10 k //= 10 return total ``` When the function is called with \(n = 50\), what value is returned?

Correct A. 48

B. 192

C. 78

D. 46

Correct Answer: A

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Question 9 View Details

A loan of \(\text{₦}500{,}000\) is to be repaid with equal annual payments at the end of each year for 5 years. The total of all payments made is \(\text{₦}650{,}000\). Assuming a constant annual interest rate \(r\) (expressed as a decimal), determine \(r\) as a percentage rounded to two decimal places.

A. 12.31%

B. 10.58%

Correct C. 9.42%

D. 8.73%

Correct Answer: C

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Question 10 View Details

A communication channel transmits 8‑bit characters. Each bit is flipped independently with probability \(0.01\).\n(i) What is the probability that a transmitted character is received without any error?\n(ii) For a file containing 10,000 characters, what is the expected number of error‑free characters received?

Correct A. Probability ≈ 0.9227; expected error‑free characters ≈ 9,227

B. Probability ≈ 0.9100; expected error‑free characters ≈ 9,100

C. Probability ≈ 0.9180; expected error‑free characters ≈ 9,180

D. Probability ≈ 0.9250; expected error‑free characters ≈ 9,250

Correct Answer: A

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Question 11 View Details

A company wants to set up a LAN using a hierarchical star topology. Each access switch can connect to at most \(12\) computers. The company has \(250\) computers. One of the switches will serve as the core switch and must be linked to the main backbone with a 10 m cable; every other switch requires a 5 m cable to the backbone. The cable from each computer to its switch is 2 m long. Assuming the minimum number of switches is used, what is the minimum total length of cable required (in metres) for the whole network?

A. 640

Correct B. 610

C. 615

D. 605

Correct Answer: B

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Question 12 View Details

A spreadsheet records the monthly sales (in thousands of naira) of a shop for a year as follows: 120, 150, 130, 160, 140, 155, 165, 170, 145, 150, 158, 162. The user creates a formula to compute the average monthly sales and then applies conditional formatting to highlight every month whose sales exceed the average. If each highlighted month will generate a separate paragraph in a Word mail‑merge document, (a) how many paragraphs will be produced, and (b) what is the combined sales of the highlighted months? Provide the answer as "x months, y".

Correct A. 6 months, 970000

B. 6 months, 950000

C. 7 months, 970000

D. 5 months, 970000

Correct Answer: A

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Question 13 View Details

A computer uses a RAID 5 array consisting of 5 disks, each having a capacity of \(1.2\) TB. What is the total usable storage capacity of the array (in TB)?

Correct A. 4.8

B. 6.0

C. 3.6

D. 5.0

Correct Answer: A

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Question 14 View Details

A desktop system contains the following components with their typical power consumptions: CPU \(95\) W, GPU \(150\) W, two hard‑disk drives each \(10\) W, one solid‑state drive \(5\) W, three case fans each \(3\) W, and motherboard \(50\) W. To ensure reliable operation, the power‑supply unit (PSU) must provide at least 20 % headroom over the total estimated load and be chosen from standard ratings that increase in steps of 50 W. What is the minimum PSU rating (in watts) that satisfies these requirements?

A. 400

B. 350

C. 500

Correct D. 450

Correct Answer: D

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Question 15 View Details

A program first computes the integer part of \(\sqrt{2025}\) and stores it in the variable \(N\). It then adds together all even integers from 1 up to \(N\) inclusive and outputs the sum. What number does the program output?

A. 495

B. 528

C. 462

Correct D. 506

Correct Answer: D

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Question 16 View Details

A text file contains 3,200 characters. 70% of the characters are standard ASCII characters (which require 8 bits each), while the remaining characters are from the extended Unicode set and require 24 bits each. The file is then compressed using a lossless algorithm that reduces the total size by \(18\%\). Calculate the final size of the file in kilobytes (1\,KB = 1024\,bytes), rounded to two decimal places.

Correct A. 4.10 KB

B. 4.50 KB

C. 5.12 KB

D. 3.84 KB

Correct Answer: A

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Question 17 View Details

What is the primary function of the motherboard in a computer system?

Correct A. It connects and enables communication among all computer components.

B. It stores all data and programs for the computer.

C. It performs all the computational processing tasks.

D. It supplies power to all the computer components.

Correct Answer: A

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Question 18 View Details

A company stores user passwords as salted SHA‑256 hashes. For each user a unique 4‑character alphanumeric salt (each character can be an uppercase letter A‑Z or a digit 0‑9) is concatenated with the password before hashing. An attacker obtains the database containing usernames, salts and the corresponding hash values. Explain why the attacker cannot directly recover the original passwords. Then, assuming a password is known to be exactly six lowercase letters (a‑z), calculate the total number of possible salted‑hash inputs that the attacker would have to try for a single user.

Correct A. 518,859,880,022,016

B. 5,188,598,800,220,160

C. 14,412,774,445,056

D. 19,956,149,231,616

Correct Answer: A

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Question 19 View Details

Who is credited with designing the first mechanical computer known as the Analytical Engine?

A. Ada Lovelace

Correct B. Charles Babbage

C. John von Neumann

D. Alan Turing

Correct Answer: B

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Question 20 View Details

An organization assesses three threat categories with the following annual occurrence probabilities and potential monetary impacts: Malware (probability \(0.20\), impact \(\text{₦}2{,}000{,}000\)), Insider abuse (probability \(0.05\), impact \(\text{₦}5{,}000{,}000\)), and DDoS attack (probability \(0.10\), impact \(\text{₦}3{,}000{,}000\)). The organization can invest in security controls that reduce the probability of each threat by \(30\%\) per \(\text{₦}500{,}000\) spent, up to a maximum reduction of \(60\%\) per threat. With a total budget of \(\text{₦}1{,}500{,}000\), how should the funds be allocated among the three threat controls to minimise the expected annual loss? State the allocation (in \(\text{₦}\)) for each threat and the resulting minimized expected loss (in \(\text{₦}\)).

A. Malware: ₦500,000; DDoS: ₦500,000; Insider abuse: ₦500,000; Expected loss: ₦730,000

Correct B. Malware: ₦1,000,000; DDoS: ₦500,000; Insider abuse: ₦0; Expected loss: ₦620,000

C. Malware: ₦0; DDoS: ₦1,000,000; Insider abuse: ₦500,000; Expected loss: ₦800,000

D. Malware: ₦1,500,000; DDoS: ₦0; Insider abuse: ₦0; Expected loss: ₦560,000

Correct Answer: B

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Question 21 View Details

Consider the following CSS rules applied to a <div> element with id="box" and classes "content highlight": #box { width:200px; padding:10px; border:5px solid black; margin:15px; box-sizing:content-box; background:#f0f0f0; } .content { width:180px; padding:20px; border:2px solid red; box-sizing:border-box; background:#c0c0c0; } .highlight { width:150px; padding:5px; border:1px solid blue; box-sizing:content-box; background:#a0a0a0; } Using CSS cascade and box‑model rules, determine (a) the total horizontal space (margin + border + padding + content) occupied by the element when rendered, in pixels, and (b) the final background colour that will be displayed. Provide your answer as "<space> px; <colour>".

A. 192 px; #a0a0a0

B. 210 px; #c0c0c0

Correct C. 260 px; #f0f0f0

D. 260 px; #c0c0c0

Correct Answer: C

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Question 22 View Details

A class of 40 students took a test. The score distribution is: 5 students scored 40, 8 scored 55, 12 scored 70, 10 scored 85, and 5 scored 100. (a) What is the median score? (b) What percentage of students scored above the median? (c) The teacher wants at least 60% of the class to score above the median after adding the same integer number of points to every student's score (no score may exceed 100). What is the minimum number of points that must be added? If it is impossible, state so.

A. Feasible

Correct B. Impossible

C. Possible

D. Achievable

Correct Answer: B

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Question 23 View Details

A disk uses a block size of 4\,KiB. Four files occupy the following byte sizes: File A - 6,500 bytes, File B - 12,300 bytes, File C - 3,200 bytes, File D - 9,800 bytes. (a) How many disk blocks are required in total? (b) What is the total wasted space (unused bytes within allocated blocks)? (c) If the average seek time is 8 ms, rotational latency is 4.2 ms, and transfer time per block is 0.5 ms, compute the total time to read all files sequentially (assume one seek and one rotational latency per file, no caching). Give the answer in milliseconds rounded to one decimal place.

Correct A. 10 blocks; 9160 bytes; 53.8 ms

B. 9 blocks; 8000 bytes; 49.5 ms

C. 10 blocks; 9500 bytes; 55.3 ms

D. 11 blocks; 10240 bytes; 58.0 ms

Correct Answer: A

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Question 24 View Details

An organisation faces an annual data‑breach probability of 0.12. External attacks account for 70\% of breaches and internal threats for 30\%. Two security measures are considered (only one can be implemented): (i) AES‑128 encryption reduces the probability of a breach caused by cryptographic attack to 0.02 per year, with other causes unchanged; (ii) a firewall blocks 95\% of external attacks, leaving internal threats unchanged. Assuming the entire external breach probability is due to cryptographic attack, compute (a) the annual breach probability if AES‑128 is implemented, (b) the annual breach probability if the firewall is implemented, and (c) which measure yields the lower breach probability. Give answers rounded to four decimal places.

A. 0.0580; 0.0402; firewall

B. 0.0560; 0.0402; AES‑128

Correct C. 0.0560; 0.0402; firewall

D. 0.0560; 0.0475; firewall

Correct Answer: C

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Question 25 View Details

A webpage uses a flex container of width \(1200\) px. The CSS is: .container { display:flex; width:1200px; } .item { flex-basis:300px; flex-grow:1; flex-shrink:2; margin:10px; } A media query for screens with max‑width \(800\) px changes the rules to: .container { flex-direction:column; } .item { flex-basis:100\%; margin:5px 0; } (a) For a screen width of \(1200\) px (no media query), what is the width of each flex item after layout, including its horizontal margins? (b) For a screen width of \(750\) px (media query active), each item's content height is \(200\) px and there is no padding or border. What total vertical space do the three items occupy, including their vertical margins? Give answers in pixels.

Correct A. 400 px; 630 px

B. 500 px; 720 px

C. 300 px; 630 px

D. 400 px; 540 px

Correct Answer: A

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