AP CSA Unit 4.2: Array Averaging with Enhanced For Loop Practice
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Unit 4, Section 4.2
Day 2 Practice • January 8, 2026
🎯 Focus: Data Sets and Averaging
Practice Question
Consider the following code segment:
int[] temps = {72, 68, 75, 80, 77};
int sum = 0;
for (int t : temps) {
sum += t;
}
double avg = (double) sum / temps.length;
System.out.println(avg);What is printed as a result of executing this code segment?
What This Tests: Section 4.2 covers working with data sets. This question tests the enhanced for loop for array traversal and the proper technique for calculating an average with double division.
Step-by-Step Trace
| Iteration | t | sum += t | sum |
|---|---|---|---|
| 1 | 72 | 0 + 72 | 72 |
| 2 | 68 | 72 + 68 | 140 |
| 3 | 75 | 140 + 75 | 215 |
| 4 | 80 | 215 + 80 | 295 |
| 5 | 77 | 295 + 77 | 372 |
Average: (double) 372 / 5 = 74.4
Key Concept: Casting for Division
// Without cast: integer division!
double avg = sum / temps.length; // 372/5 = 74 → 74.0
// With cast: true division
double avg = (double) sum / temps.length; // 372.0/5 = 74.4Common Mistakes
Mistake: Answer A (74.0)
This would be correct WITHOUT the cast. But (double) sum converts 372 to 372.0 before dividing, giving 74.4, not 74.0.
Mistake: Answer D (372)
This is the sum, not the average. Don't forget to divide by temps.length!
Enhanced For Loop
for-each Syntax
for (int t : temps) means "for each int t in temps"
Use when you need to READ all elements but don't need the index.
Cannot modify array elements with enhanced for loop!
Difficulty: Medium • Time: 3 minutes • AP Skill: 2.D - Traverse arrays
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