Practice neco data_processing 2018 Past Questions

Question 1 View Details

Company X processes 2,000 GB of data each year. It can choose between two encryption options.\n\nOption A: AES with a baseline key length of $128$ bits. The baseline processing time per transaction is 100 ms. For every additional 8 bits of key length, processing time increases by $0.3\%$ and the annual licensing fee rises by ₦0.02 per GB.\n\nOption B: Triple DES with a fixed key length of 168 bits. Its processing time per transaction is 130 ms and the licensing fee is ₦0.01 per GB per year.\n\nCompany policy requires that the processing‑time increase relative to the AES baseline must not exceed $5\%$ and that the total annual licensing cost must not exceed $5{,}000$ ₦.\n\nWhich option satisfies both constraints, and what key length (in bits) should be used for that option?

A. AES, 240 bits

B. Triple DES, 168 bits

Correct C. AES, 253 bits

D. AES, 256 bits

Correct Answer: C

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Question 2 View Details

A text file contains $1{,}500$ characters. In UTF‑8 encoding, an ASCII character occupies 1 byte while a non‑ASCII character occupies 2 bytes. If $30\%$ of the characters are non‑ASCII, what is the total storage required for the file in kilobytes (KB), rounded up to the nearest whole KB?

Correct A. 2

B. 1

C. 3

D. 5

Correct Answer: A

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Question 3 View Details

A company faces a potential insider data‑theft risk. Without any preventive measure, the probability of a theft occurring in a year is $0.02$ and the estimated loss per incident is $\$200{,}000$.\n\nTwo preventive measures are available:\n\n1. Monitoring system - reduces the theft probability to $0.005$ but costs $\$8{,}000$ per year.\n2. Employee‑training program - reduces the loss per incident by 30 % (to $\$140{,}000$) and costs $\$3{,}000$ per year.\n\nThe measures can be implemented separately or together. Assuming the effects are independent, which combination of measures (none, monitoring only, training only, both) yields the lowest expected total annual cost (sum of implementation cost and expected loss)?

A. Training only

B. Monitoring only

Correct C. None (no measures)

D. Both measures

Correct Answer: C

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Question 4 View Details

A file of size $10{,}200$ bytes is stored on a disk that uses a block size of $4{,}096$ bytes with contiguous allocation. Determine the number of blocks allocated to the file and the total amount of wasted space (internal fragmentation) in bytes.

Correct A. 2088

B. 3072

C. 1024

D. 4096

Correct Answer: A

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Question 5 View Details

A file of size $25{,}000$ bytes is to be stored on a disk with block size $1{,}024$ bytes.\n\n- In linked allocation each block stores its data plus a $4$-byte pointer to the next block.\n- In indexed allocation an index block can hold up to $128$ pointers, each pointer occupying $8$ bytes; the index block itself occupies one full block.\n\nCalculate the total storage required (data blocks plus any pointer storage) for each method and state which method uses less space.

A. Linked allocation; 24,672 bytes vs 26,624 bytes for indexed allocation

Correct B. Linked allocation; 25,700 bytes vs 26,624 bytes for indexed allocation

C. Linked allocation; 25,600 bytes vs 26,624 bytes for indexed allocation

D. Linked allocation; 25,700 bytes vs 27,200 bytes for indexed allocation

Correct Answer: B

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Question 6 View Details

A small business uses a spreadsheet to compute its monthly electricity bill. The bill is calculated as a base charge of $5,000$ naira plus $0.12$ naira per kWh for the first 500 kWh and $0.15$ naira per kWh for any consumption above 500 kWh. If the monthly consumption exceeds 800 kWh, a 10% discount is applied to the subtotal, after which the amount is rounded to the nearest hundred naira before a 5% VAT is added. For a consumption of $950$ kWh, what is the final amount payable (in naira)?

A. 4845

B. 5355

C. 4935

Correct D. 4830

Correct Answer: D

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Question 7 View Details

A data set contains $12$ numbers whose mean is $15$. The sum of the first $5$ numbers is $70$. What is the sum of the remaining $7$ numbers?

A. 100

B. 120

Correct C. 110

D. 130

Correct Answer: C

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Question 8 View Details

A computer uses a block size of $4,096$ bytes. File A is $9,800$ bytes and is stored using contiguous allocation. File B is $15,300$ bytes and is stored using linked allocation, where each block reserves $8$ bytes for a pointer. Determine (i) the total number of blocks required for both files and (ii) the total internal‑fragmentation waste for File A only (in bytes).

Correct A. 7 blocks, 2,488 bytes

B. 8 blocks, 2,488 bytes

C. 7 blocks, 2,896 bytes

D. 6 blocks, 2,488 bytes

Correct Answer: A

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Question 9 View Details

A university database has two tables: Students(SID, Name, Dept) and Enrolments(SID, CourseCode, Grade). There are $120$ students in total. Every Computer Science student (Dept = 'CS') enrols in exactly $4$ courses, while students from other departments enrol in exactly $2$ courses. If the Enrolments table contains $340$ records, how many students are not in the Computer Science department?

Correct A. 70

B. 60

C. 50

D. 80

Correct Answer: A

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Question 10 View Details

Convert the 8‑bit binary number $10110101$ to its decimal equivalent.

A. 185

B. 197

Correct C. 181

D. 173

Correct Answer: C

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Question 11 View Details

A spreadsheet contains the numbers 34, 12, 27, 5, 19, and 41 in cells A1 through A6. After sorting the range A1:A6 in ascending order, what is the second smallest number?

Correct A. 12

B. 19

C. 27

D. 5

Correct Answer: A

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Question 12 View Details

A company records quarterly sales data as follows (units sold, selling price per unit, cost per unit):\n\nQuarter\,1: $500$ units, price $\text{₦}200$, cost $\text{₦}150$\nQuarter\,2: $600$ units, price $\text{₦}210$, cost $\text{₦}155$\nQuarter\,3: $720$ units, price $\text{₦}220$, cost $\text{₦}160$\nQuarter\,4: $864$ units, price $\text{₦}230$, cost $\text{₦}165$\n\nFor each quarter, profit = units $\times$ (selling price $-$ cost).\n\nWhich quarter shows the greatest percentage increase in profit compared to the preceding quarter, and what is that percentage increase (to the nearest whole percent)?

Correct A. Quarter 2, 32%

B. Quarter 3, 31%

C. Quarter 2, 30%

D. Quarter 4, 30%

Correct Answer: A

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Question 13 View Details

In a data processing cycle, the four stages take the following times per data set: Input $15$ minutes, Processing $45$ minutes, Output $10$ minutes, Storage $5$ minutes. The Processing stage consists of Validation (which occupies $60\%$ of the processing time) and Computation (the remaining time). If a batch of $12$ data sets is processed sequentially, what is the total time spent on Validation for the entire batch (in minutes)?

A. 312

B. 360

C. 288

Correct D. 324

Correct Answer: D

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Question 14 View Details

Consider a relation R(StudentID, CourseCode, Instructor, Grade) with the functional dependencies: $StudentID, CourseCode \rightarrow Grade, Instructor$ and $CourseCode \rightarrow Instructor$. Assuming the primary key of R is $(StudentID, CourseCode)$, what is the highest normal form that R satisfies?

A. 2NF

B. 3NF

Correct C. 1NF

D. BCNF

Correct Answer: C

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Question 15 View Details

A company employs three independent security controls against cyber‑attacks:\n\n- Firewall blocks an attack with probability $0.90$;\n- Intrusion Detection System (IDS) detects an attack with probability $0.80$;\n- Employee training prevents a successful phishing attempt with probability $0.70$.\n\nAssuming an attack must bypass all three controls to succeed and that the controls operate independently,\n\na) What is the probability that a single attack succeeds?\n\nb) If the company experiences $500$ attack attempts in a year, what is the expected number of successful attacks (rounded to the nearest whole number)?

A. 0.005; 2

Correct B. 0.006; 3

C. 0.014; 7

D. 0.018; 9

Correct Answer: B

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Question 16 View Details

An enterprise currently stores its data locally. The local storage incurs a fixed monthly cost of N8,000 and a variable cost of N0.30 per gigabyte (GB) of data stored. The amount of data stored at the start of month 1 is 200 GB and grows by 10 % each month (compounded). The enterprise is considering a cloud storage service that charges a fixed monthly subscription of N5,000 plus N0.80 per GB of data stored each month. Assuming the data growth pattern is the same under either option, determine the smallest integer month $n$ (starting from month 1) at which the cumulative cost of using the cloud service becomes less than the cumulative cost of local storage.

Correct A. 54

B. 60

C. 52

D. 48

Correct Answer: A

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Question 17 View Details

Given the Boolean function $F = (A + B')(C'D + AB)$, simplify the expression to its minimal sum‑of‑products form and then implement the simplified function using only two‑input NAND gates. What is the minimum number of NAND gates required for the implementation?

Correct A. 15

B. 16

C. 13

D. 18

Correct Answer: A

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Question 18 View Details

During a batch data‑processing run, 1 500 records are input. In the first processing stage, 5 % of the records are flagged as erroneous and sent back for correction. After correction, 3 % of the original records are still erroneous and are discarded. The corrected records (those that were flagged) are then processed a second time; in this second processing stage, 2 % of the corrected records are again flagged for correction, and after this second correction 1 % of the original records are finally discarded. Assuming all flagged records are successfully corrected after each stage, how many records are finally stored at the end of the cycle?

A. 1425

B. 1455

C. 1445

Correct D. 1440

Correct Answer: D

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Question 19 View Details

An academic spreadsheet records a student's marks (out of 100) in cells B2:B6 and the corresponding credit units in cells C2:C6 as follows: | Subject | Marks (B) | Credits (C) | |---|---|---| | A | 78 | 3 | | B | 65 | 2 | | C | 58 | 4 | | D | 48 | 2 | | E | 42 | 3 | The grade point for each subject is assigned according to the table: - 70 - 100 → 5 points - 60 - 69 → 4 points - 50 - 59 → 3 points - 45 - 49 → 2 points - 40 - 44 → 1 point - below 40 → 0 point Write a single spreadsheet formula (using only built‑in functions and no helper columns) that computes the weighted grade point average (GPA) defined as $\displaystyle \frac{\sum (\text{grade point} \times \text{credit})}{\sum \text{credit}}$. Then calculate the GPA for the data above and state whether the student qualifies for honors (GPA ≥ 4.5).

Correct A. GPA = 3.00; does not qualify for honors

B. GPA = 3.00; qualifies for honors

C. GPA = 3.33; does not qualify for honors

D. GPA = 2.80; does not qualify for honors

Correct Answer: A

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Question 20 View Details

In a data‑processing system the following decision rule is applied after each processing cycle: if the number of records successfully processed is greater than 80 % of the total input records, the cycle terminates; otherwise the system repeats the processing after correcting the flagged records. For a batch of 2 000 input records, the first processing cycle yields 1 500 successfully processed records, 300 records are flagged for correction, and 200 records are lost due to corruption. After correction, 90 % of the flagged records become correct. Will the system repeat the processing cycle after the first correction? Justify your answer with calculations.

A. Yes, the system will repeat the cycle

Correct B. No, the system will not repeat the cycle

C. No, the system will repeat the cycle

D. Yes, the system will not repeat the cycle

Correct Answer: B

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Question 21 View Details

A set of test scores is grouped into intervals of width 10 as shown below. The frequencies for the first nine intervals are: $0\text{-}9$: 5, $10\text{-}19$: 7, $20\text{-}29$: 9, $30\text{-}39$: 11, $40\text{-}49$: 13, $50\text{-}59$: 15, $60\text{-}69$: 17, $70\text{-}79$: 19, $80\text{-}89$: 21. The frequency for the last interval $90\text{-}99$ is unknown. If the overall mean score of the 124 students is 57, determine the missing frequency.

A. 5

Correct B. 7

C. 12

D. 9

Correct Answer: B

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Question 22 View Details

The following data give the quarterly sales (in units) for four products:\nProduct P1: Q1=200, Q2=250, Q3=300, Q4=800;\nProduct P2: Q1=500, Q2=450, Q3=400, Q4=600;\nProduct P3: Q1=150, Q2=180, Q3=170, Q4=400;\nProduct P4: Q1=300, Q2=320, Q3=310, Q4=900.\nA commission of 5\% of the Q4 sales is paid to a product only if its Q4 sales exceed both (i) the average of its own Q1-Q3 sales and (ii) the overall average Q4 sales of all products. Calculate the total commission payable.

A. 95

B. 105

Correct C. 85

D. 75

Correct Answer: C

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Question 23 View Details

Consider a relation $R(A,B,C)$ with the functional dependencies $A \rightarrow B$ and $B \rightarrow C$. Decompose $R$ into a set of relations that are in Boyce‑Codd Normal Form (BCNF) while preserving dependencies and ensuring a lossless‑join. List the resulting relations.

A. R1(A,C) and R2(A,B)

B. R1(A,B) and R2(A,C)

C. R1(A,B) and R2(B,C)

Correct D. R1(B,C) and R2(A,B)

Correct Answer: D

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Question 24 View Details

The data‑processing cycle consists of the following four activities: (a) Data presentation, (b) Data collection, (c) Data analysis, (d) Data validation. Write the activities in their correct chronological order using the letters.

Correct A. b, d, c, a

B. b, c, d, a

C. d, b, c, a

D. a, b, c, d

Correct Answer: A

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Question 25 View Details

The EMP table contains the columns EmpID, Dept and Salary with the following rows:\nEmpID 1: Dept = Sales, Salary = 50000\nEmpID 2: Dept = Sales, Salary = 60000\nEmpID 3: Dept = HR, Salary = 55000\nEmpID 4: Dept = HR, Salary = 70000\nEmpID 5: Dept = IT, Salary = 80000\nEmpID 6: Dept = IT, Salary = 90000\nWhat is the average Salary of the department(s) that have the highest average Salary?

A. 55000

B. 62500

C. 80000

Correct D. 85000

Correct Answer: D

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