CHALLENGE 2: Type Safety with Arrays
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SOLUTION:

function calculateAverage(scores: number[]): number {
  const sum = scores.reduce((total, score) => total + score, 0);
  return sum / scores.length;
}

// Testing:
const studentScores: number[] = [95, 87, 92, 88, 90];
const average = calculateAverage(studentScores);
console.log(average);  // Output: 90.4

EXPLANATION:
- "scores: number[]" — parameter accepts an array of numbers
- ": number" (after closing paren) — function returns a number
- The reduce() method sums all values
- Dividing by length gives the average

ALTERNATIVE SOLUTION (simpler):

function calculateAverage(scores: number[]): number {
  if (scores.length === 0) return 0;
  const sum = scores.reduce((a, b) => a + b, 0);
  return sum / scores.length;
}

WHY TYPE ANNOTATIONS MATTER HERE:
- TypeScript ensures only numbers are passed
- calculateAverage([95, 87, 92])  ✅ Works
- calculateAverage([95, "87", 92])  ❌ Error! "87" is a string, not a number
- The IDE knows the function returns a number, so the caller knows what to expect

EDGE CASES:
- Empty array: returns 0 (handled by the if check in alternative)
- Single element: returns that element
- Negative numbers: works fine