I took the 2020 Practice Exam 1 MCQ in Collegeboard and got a 60/67. Here are all the questions I got wrong:
Question 11
A color in a computing application is represented by an RGB triplet that describes the amount of red, green, and blue, respectively, used to create the desired color. A selection of colors and their corresponding RGB triplets are shown in the following table. Each value is represented in decimal (base 10).
According to information in the table, what color is represented by the binary RGB triplet (11111111, 11111111, 11110000) ?
I chose: D, Correct Answer: A
I thought (11111111, 11111111, 11110000) was vivid yellow (255, 255, 14), but its correct decimal value is (255, 255, 240), which corresponds to ivory, so ivory is the correct answer.
Question 12
A color in a computing application is represented by an RGB triplet that describes the amount of red, green, and blue, respectively, used to create the desired color. A selection of colors and their corresponding RGB triplets are shown in the following table. Each value is represented in decimal (base 10).
What is the binary RGB triplet for the color indigo?
I chose: A, Correct Answer: C
I thought that the binary representation of indigo (75, 0, 130) was equal to (00100101, 00000000, 10000010). Instead, C (01001011, 00000000, 10000010) correctly represents indigo.
Question 26
A list of binary values (0 or 1) is used to represent a black-and-white image. Which of the following is LEAST likely to be stored as metadata associated with the image?
I chose: A, Correct answer: D
I chose A (Copyright information for the image) because I thought that copyright information was not likely to be stored as metadata for an image, but instead D (A Duplicate copy of the data) is actually not metadata for an image.
Question 40
Which of the following best explains how a certificate authority is used in protecting data?
I chose: A, Correct answer: D
I chose A because I thought that a certificate authority would verify the safety of websites, ensuring that user data is protected. But instead D is correct since it verifies encryption key authenticity.
Question 47
The procedure BinarySearch (numList, target) correctly implements a binary search algorithm on the list of numbers numList. The procedure returns an index where target occurs in numList, or -1 if target does not occur in numList.
Which of the following conditions must be met in order for the procedure to work as intended?
I chose: B, Correct answer: C
I chose B because I thought that a binary search won’t work if the list has duplicate values. I should have chosen C because a list must be sorted in order for a binary search to work.
Question 50
Consider the following algorithms. Each algorithm operates on a list containing n elements, where n is a very large integer.
I. An algorithm that accesses each element in the list twice
II. An algorithm that accesses each element in the list n times
III. An algorithm that accesses only the first 10 elements in the list, regardless of the size of the list
Which of the algorithms run in reasonable time?
I chose: B, Correct Answer: D
I chose B because I only thought that Algorithm III ran in reasonable time. I should have chosen D (I, II, and III) because all the algorithms work in reasonable time since all three are less than the time complexity limit.
Question 67
The procedure NumOccurrences is intended to count and return the number of times targetWord appears in the list wordList. The procedure does not work as intended.
For which of the following code segments will the call to NumOccurrences NOT return the intended value? Select two answers.
I chose: D, Correct answer: A, B
I chose D because I misread the question. Also, I didn’t see that it said to select two answers. I should have chosen A and B because they both have words that appear in the list, but incorrectly return 0.
Conclusion
In conclusion, I performed well in programming topics like conditionals, boolean expressions, iteration, and program design and development. However, I need to improve in binary numbers, binary search, and time complexity. This MCQ made me realize I need to work on computer science theory such as binary and time complexity, so I will review these topics using Collegeboard and online resources.