Practice neco data_processing 2020 Past Questions

Question 1 View Details

A small business wants to reduce its overall security risk by at least 70\% (i.e., the remaining risk must be at most 30\% of the original). It can implement the following security measures, each with a fixed cost and a risk‑reduction factor that multiplies the remaining risk:\n\n- Firewall: cost ₦200, reduces risk by 30\% (remaining factor 0.70)\n- Antivirus software: cost ₦150, reduces risk by 20\% (remaining factor 0.80)\n- Employee security training: cost ₦100, reduces risk by 25\% (remaining factor 0.75)\n- Data encryption: cost ₦180, reduces risk by 35\% (remaining factor 0.65)\n\nThe business may choose any combination of these measures. What is the minimum total cost that will achieve the required risk reduction, and which measures must be selected?

Correct A. ₦630 (all four measures)

B. ₦380 (firewall, data encryption)

C. ₦450 (firewall, antivirus, employee security training)

D. ₦430 (antivirus, employee security training, data encryption)

Correct Answer: A

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Question 2 View Details

In a spreadsheet, column A contains employee IDs, column B the number of hours worked, and column C the hourly rate (₦ per hour). Column D should calculate the gross pay for each employee, adding a 10\% bonus to the gross pay if the employee ID starts with the letter "M". Write a formula that can be entered in D2 and copied down to achieve this, and then compute the total gross pay for the four employees listed below.\n\nA2: M101, B2: 40, C2: 15\nA3: A202, B3: 35, C3: 14\nA4: M103, B4: 45, C4: 16\nA5: B304, B5: 30, C5: 13

A. 2200

B. 2260

C. 2420

Correct D. 2332

Correct Answer: D

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Question 3 View Details

Consider two relations R(A,B,C) and S(B,D). Relation R contains 120 tuples, of which 45 satisfy the condition C\>10. Among these 45 tuples, the values of attribute B are distributed as follows: B=1 occurs 10 times, B=2 occurs 15 times, B=3 occurs 20 times. Relation S consists of three tuples: (1, x), (2, y) and (4, z). How many tuples are produced by the relational algebra expression \( \pi_{A}\bigl(\sigma_{C>10}(R)\bigr) \;\Join_{B}\; S \) ?

Correct A. 25

B. 45

C. 20

D. 30

Correct Answer: A

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Question 4 View Details

A teacher wants to convert raw exam scores (out of 100) to a 5‑point grading scale using a linear transformation of the form \( \text{grade}=a\cdot\text{score}+b \). The transformation must map a score of 0 to a grade of 0 and a score of 100 to a grade of 5. Determine the values of \(a\) and \(b\). Then, using this transformation, find the average grade for a student who scored 78 in Mathematics, 85 in English and 92 in Science.

A. 4.15

Correct B. 4.25

C. 4.75

D. 3.95

Correct Answer: B

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Question 5 View Details

The following tables store information about a company.\n\nEmployees(EmpID, DeptID, Salary)\n\nDeptID | DeptName | ManagerID\n1 | Administration | 10\n2 | Sales | 12\n3 | Research | 15\n\nThe Employees table contains these records:\n\nEmpID DeptID Salary\n101 1 5000\n102 1 6000\n103 1 5500\n201 2 4000\n202 2 4500\n203 2 4200\n204 2 4600\n301 3 7000\n302 3 8000\n303 3 7500\n304 3 7200\n305 3 7700\n\nFind the name of the department whose average employee salary is greater than the overall average salary of the company and that has more than three employees.

A. Administration

B. Finance

C. Sales

Correct D. Research

Correct Answer: D

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Question 6 View Details

In a survey of 120 households, the following information was recorded for each household: (i) the type of dwelling (detached, semi-detached, apartment), (ii) the number of occupants, (iii) whether the household has internet access (yes/no). Classify each of the three variables as either qualitative (categorical) or quantitative (numerical).

A. (i) quantitative, (ii) qualitative, (iii) quantitative

Correct B. (i) qualitative, (ii) quantitative, (iii) qualitative

C. (i) quantitative, (ii) quantitative, (iii) qualitative

D. (i) qualitative, (ii) qualitative, (iii) quantitative

Correct Answer: B

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Question 7 View Details

A data processing system consists of four stages: Input, Processing, Storage, and Output. The Input stage takes \(5\) minutes. The Processing stage takes twice the time taken by the Input stage plus \(3\) minutes. The Storage stage takes half the time taken by the Processing stage. The Output stage takes \(4\) minutes more than the Storage stage. What is the total time, in minutes, required to complete one full cycle?

A. 34

B. 40

C. 36

Correct D. 35

Correct Answer: D

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Question 8 View Details

A small business keeps its accounts manually. The manual ledger costs \(N200\) per month for paper and \(N150\) per month for staff time, giving a total manual cost of \(N350\) per month. The business is considering switching to spreadsheet software that requires a one‑time purchase of \(N5000\) and a monthly subscription of \(N200\) for the first six months. After the first six months the subscription fee is reduced by 10\% (i.e., it becomes \(N180\) per month). After how many whole months will the total cost of using the software become cheaper than continuing with the manual ledger?

Correct A. 31

B. 30

C. 35

D. 32

Correct Answer: A

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Question 9 View Details

A teacher records the scores of eight students in a test: 70, 85, 78, 92, 88, 76, 81, 90. By mistake, the score 78 was entered as 87. Using the erroneous data set, the average score was calculated. What is the correct average score after correcting the error?

Correct A. 82.5

B. 83.6

C. 84.0

D. 81.5

Correct Answer: A

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Question 10 View Details

An organisation assesses three security threats using a weighted risk‑score formula: \(\text{Risk score}=0.6\times\text{Likelihood}+0.4\times\text{Impact}\). The likelihood and impact of each threat are rated as Low=1, Medium=2, High=3. The threats are:\n- Malware: Likelihood High, Impact Medium\n- Data breach: Likelihood Medium, Impact High\n- Insider theft: Likelihood Low, Impact High\nCalculate the risk score for each threat and list the threats in order from highest to lowest risk.

Correct A. Malware, Data breach, Insider theft

B. Malware, Insider theft, Data breach

C. Insider theft, Malware, Data breach

D. Data breach, Malware, Insider theft

Correct Answer: A

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Question 11 View Details

Consider a relation R(A,B,C,D) with functional dependencies: A \rightarrow B, BC \rightarrow D, and D \rightarrow A. (a) List all candidate keys of R. (b) Decompose R into BCNF. How many relations result from the decomposition?

A. Candidate keys: A, B, C; Number of BCNF relations: 2

B. Candidate keys: AB, AD, BD; Number of BCNF relations: 4

Correct C. Candidate keys: AC, BC, CD; Number of BCNF relations: 3

D. Candidate keys: AC, BD, CD; Number of BCNF relations: 5

Correct Answer: C

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Question 12 View Details

An unindexed file contains 10,000 records, each 100 bytes. The block size is 512 bytes. A B+\-tree index of order 100 is built on the file. (a) How many block reads are required, on average, to locate a record by sequential search? (b) How many block reads are needed using the index? (c) Which method is faster for record retrieval?

Correct A. Sequential average reads: 1001 blocks; Index reads: 2 blocks; Indexing is faster

B. Sequential average reads: 1001 blocks; Index reads: 5 blocks; Indexing is faster

C. Sequential average reads: 2000 blocks; Index reads: 2 blocks; Indexing is faster

D. Sequential average reads: 1001 blocks; Index reads: 2 blocks; Sequential search is faster

Correct Answer: A

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Question 13 View Details

State the four main stages of the data\-processing cycle.

A. Collection, Processing, Storage, Distribution

B. Input, Processing, Retrieval, Output

Correct C. Input, Processing, Storage, Output

D. Input, Analysis, Storage, Output

Correct Answer: C

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Question 14 View Details

A file contains 5,000 records each 120 bytes. The block size is 512 bytes. (a) Determine the total storage required when the file is stored sequentially with fixed\-length blocks. (b) If an indexed\-sequential organization is used, where each index block can hold 64 entries (each entry 8 bytes), compute the total storage required (data blocks plus index blocks). (c) Which organization uses less storage?

Correct A. Sequential uses less storage (640,000 bytes) compared with indexed\-sequential (680,448 bytes)

B. Sequential uses less storage (640,000 bytes) compared with indexed\-sequential (690,000 bytes)

C. Sequential uses less storage (650,000 bytes) compared with indexed\-sequential (670,000 bytes)

D. Indexed\-sequential uses less storage (660,000 bytes) compared with sequential (640,000 bytes)

Correct Answer: A

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Question 15 View Details

Given the Boolean function \(F(A,B,C,D)=\Sigma m(1,3,4,6,9,11,12,14)\): (a) Find a minimal sum\-of\-products expression for \(F\). (b) Using only two\-input NAND gates, what is the minimum number of gates required to implement \(F\)?

A. Minimal SOP: \overline{A}D + A\overline{D}; Minimum NAND gates: 5

B. Minimal SOP: \overline{B}D + BC; Minimum NAND gates: 6

C. Minimal SOP: \overline{B}C + B\overline{C}; Minimum NAND gates: 3

Correct D. Minimal SOP: \overline{B}D + B\overline{D}; Minimum NAND gates: 4

Correct Answer: D

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Question 16 View Details

A company allocates its ICT budget of ₦500,000 across the data processing cycle as follows: \(30\%\) for data collection, \(25\%\) for processing, \(20\%\) for storage and the remainder for dissemination. Management decides to reduce the dissemination allocation by \(10\%\) of its original amount and to distribute the saved amount equally between collection and processing. What are the new percentage allocations for collection, processing, storage and dissemination after this re‑allocation?

Correct A. Collection 31.25 %, Processing 26.25 %, Storage 20 %, Dissemination 22.5 %

B. Collection 31.25 %, Processing 26.25 %, Storage 22.5 %, Dissemination 20 %

C. Collection 32.5 %, Processing 27.5 %, Storage 20 %, Dissemination 20 %

D. Collection 30.5 %, Processing 25.5 %, Storage 20 %, Dissemination 24 %

Correct Answer: A

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Question 17 View Details

In a data entry system each record consists of 5 independent fields. The probability that a single field is entered incorrectly is \(0.02\). A batch contains 200 records. (a) What is the expected number of records that contain at least one error? (b) If a quality‑control step detects and corrects \(80\%\) of the erroneous records, how many records are expected to be released without error after the QC?

A. ≈ 194.5 records (rounded to one decimal place)

B. ≈ 198.0 records (rounded to one decimal place)

C. ≈ 200.0 records (rounded to one decimal place)

Correct D. ≈ 196.2 records (rounded to one decimal place)

Correct Answer: D

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Question 18 View Details

A small business currently stores 2 TB of data on local hard drives. Each 1‑TB drive costs \(\text{₦}120,000\) and has a lifespan of 3 years; annual maintenance per drive is \(\text{₦}5,000\). Data volume grows by \(20\%\) each year. Alternatively, the business can use a cloud service that charges \(\text{₦}15,000\) per TB per month with no maintenance. Assuming the business must have enough storage for the data each year, which option (local drives or cloud service) has the lower total cost over the three‑year period? Show the total cost for each option.

A. Cloud storage is cheaper; total cost \\(\\text{₦}480,000\) (local would cost \\(\\text{₦}1,200,000\)).

Correct B. Local storage is cheaper; total cost \(\text{₦}540,000\) (cloud would cost \(\text{₦}1,572,480\)).

C. Local storage is cheaper; total cost \\(\\text{₦}600,000\) (cloud would cost \\(\\text{₦}1,500,000\)).

D. Both options cost the same; total cost \\(\\text{₦}540,000\) each.

Correct Answer: B

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Question 19 View Details

A file of size 2000 KB is stored on a disk whose block size is 4 KB. (a) If the file is stored contiguously, the read time is 5 ms per block plus 0.01 ms per KB of data transferred. (b) If the same file is fragmented into 5 non‑contiguous fragments, an additional seek time of 2 ms is incurred for each fragment. Which storage method yields the shorter total read time? State the total read time for each method and indicate the faster one.

A. Contiguous: 2500 ms, Fragmented: 2550 ms - contiguous is faster

Correct B. Contiguous: 2520 ms, Fragmented: 2530 ms - contiguous is faster

C. Contiguous: 2530 ms, Fragmented: 2520 ms - fragmented is faster

D. Contiguous: 2600 ms, Fragmented: 2600 ms - both are equal

Correct Answer: B

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Question 20 View Details

In a spreadsheet, column A lists months 1-12 and column B contains the corresponding sales figures (in units): 120, 150, 180, 210, 190, 230, 250, 240, 260, 300, 310, 330. A 3‑month moving average is calculated for months 3-12 using the formula =AVERAGE(Bn‑2:Bn). Conditional formatting is set to highlight a month when its sales exceed the moving average by more than \(15\%\). How many months will be highlighted by this conditional formatting?

A. 1

B. 4

Correct C. 2

D. 3

Correct Answer: C

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Question 21 View Details

A computer stores the decimal number \(45_{10}\) in an 8‑bit unsigned binary format. What is the hexadecimal representation of this number?

A. 3D

B. 2E

C. 2C

Correct D. 2D

Correct Answer: D

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Question 22 View Details

A data set contains five numbers whose mean is \(12\). After removing the smallest number the mean of the remaining four numbers becomes \(13\). What was the smallest number?

A. 12

B. 6

C. 10

Correct D. 8

Correct Answer: D

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Question 23 View Details

A spreadsheet lists three items with their quantities and unit prices: Item A - quantity \(120\), unit price \(\text{₦}250\); Item B - quantity \(80\), unit price \(\text{₦}340\); Item C - quantity \(150\), unit price \(\text{₦}210\). The total cost is first increased by a 5\% tax, then a 10\% discount is applied to the taxed amount. The resulting amount is sold at a uniform selling price of \(\text{₦}300\) per unit (total units = sum of quantities). What is the profit earned?

A. 12308.5

Correct B. 21178.5

C. 25170.0

D. 11865.0

Correct Answer: B

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Question 24 View Details

In a spreadsheet, five students have coursework (C) and exam (E) scores as follows: S1: C=78, E=85; S2: C=82, E=79; S3: C=69, E=92; S4: C=88, E=73; S5: C=74, E=88. The final grade is calculated as \(0.4\times C + 0.6\times E\). Which student obtains the highest final grade and what is that grade?

A. S5 with a final grade of 82.4

Correct B. S3 with a final grade of 82.8

C. S1 with a final grade of 82.2

D. S2 with a final grade of 80.2

Correct Answer: B

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Question 25 View Details

A disk uses a block size of \(4\text{ KB}\). Three files are stored: a text file of \(9{,}500\) bytes, an image file of \(2.3\) MB, and a video file of \(15.7\) MB. Each file occupies whole blocks (no sharing). Determine the total number of blocks required and the total wasted space (unused bytes in the last block of each file).

Correct A. 4612 blocks, 6884 bytes wasted

B. 4609 blocks, 6884 bytes wasted

C. 4615 blocks, 6884 bytes wasted

D. 4612 blocks, 7200 bytes wasted

Correct Answer: A

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