Questions: Step-by-Step Instructions (Algorithms)

Question 1

A recipe says: (1) Preheat oven. (2) Mix ingredients. (3) Pour batter in pan. (4) Bake for 30 minutes. (5) Let cool. What would happen if you did step 4 before step 2?

• A. Nothing — the order does not matter
• B. You would bake an empty pan because you have not mixed or poured the batter yet
• C. The recipe would work fine, just in a different order
• D. You would need to preheat longer

Answer: (B)

If you bake (step 4) before mixing ingredients (step 2), the pan would be empty (or not even have batter poured in). The recipe fails because later steps depend on earlier steps being complete. This is why order matters in algorithms: each step may depend on the results of previous steps.

Question 2

Which of the following is the best step in an algorithm for making a peanut butter sandwich?

• A. 'Make the sandwich' — short and clear
• B. 'Use a knife to spread peanut butter on one side of a slice of bread' — specific and actionable
• C. 'Do the peanut butter thing' — everyone knows what that means
• D. 'Put stuff on bread' — broad enough to cover any situation

Answer: (B)

Good algorithm steps are specific and actionable — anyone should be able to follow them without guessing. 'Use a knife to spread peanut butter on one side of a slice of bread' tells you the tool (knife), the action (spread), the material (peanut butter), and the location (one side of a slice of bread). The other options are too vague — they require the reader to fill in details, which can lead to different interpretations.

Question 3

An algorithm is primarily an algorithm if a computer runs it.

• T. True
• F. False

Answer: False

Algorithms existed long before computers. A recipe is an algorithm for cooking. Directions to someone's house are an algorithm for navigating. Long division is an algorithm for dividing numbers. An algorithm is any step-by-step procedure that produces a predictable result. Computers happen to be very good at following algorithms, but humans follow them every day.

Question 4

What makes a good algorithm different from just a list of ideas?

Model answer: A good algorithm has three properties that a list of ideas lacks: (1) Clear ordering — the steps must be done in a specific sequence. (2) Precision — each step is specific enough that anyone can follow it without guessing. (3) Completeness — no steps are missing. A list of ideas might say 'make a sandwich, pack lunch, go to school' — but an algorithm for making the sandwich would specify every action: 'take out two slices of bread, open the peanut butter jar, use a knife to spread...' The algorithm leaves nothing to interpretation.

These properties — ordering, precision, and completeness — are exactly what computer scientists require of algorithms. But they apply equally to human instructions. Students who learn to write clear step-by-step instructions at this stage develop a mindset that transfers directly to programming, mathematical proof-writing, and any field that requires procedural clarity.