AP CSA 1.5 Exercise 1: Class Average

Unit 1: Using Objects and Methods · Lesson 1.5 · Exercise 1

Class Average

Casting and Range of Variables. Write real Java, run it, and submit it to be graded against hidden test cases.

Back to the Lesson 1.5 page All Unit 1 lessons

Why this one is worth doing

Casting after the division is too late. This exercise prints both answers side by side so the difference is impossible to miss.

What to write

Read two integers: a total number of points and a count of students. Assume the count is not zero.
Print the integer average, computed with int division.
Print the exact average as a double, by casting BEFORE you divide.
Print the exact average again, this time truncated back to an int with a cast.

Your program reads

Two integers on separate lines: total, then count.

Your program prints

Three lines: the int division result, the exact average as a double, and that average cast back to an int.

Worked examples

These are the cases you can see. There are more you cannot, and they use different values, so an answer that prints these numbers as constants will fail.

Example 1 input

7
2

Example 1 output

3
3.5
3

Example 2 input

10
4

Example 2 output

2
2.5
2

Your answer

Main.java

import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    int total = input.nextInt();
    int count = input.nextInt();

    // Three lines. Two of them are the same division, cast differently.
  }
}

Input for the Run button

Run sends whatever is in the input box below. Submitting runs your program against every test case, including hidden ones with different input.

Stuck?

Hint 1

(double) total / count casts total first, so the division is a double division. (double) (total / count) divides as ints first and then converts the already wrong answer.

Hint 2

Casting a double to an int truncates toward zero. It does not round: (int) 3.9 is 3.

Hint 3

A double always prints with a decimal point. If your second line shows 3 instead of 3.0, you divided as ints somewhere.

Where to go next

Rework the Lesson 1.5 page Pick another Unit 1 lesson

Get in Touch

Whether you're a student, parent, or teacher — I'd love to hear from you.

Typically responds within 24 hours

✓

Message Sent!

Thanks for reaching out. I'll get back to you within 24 hours.

Name *

Email *

I am a... (optional)

Which course? (optional)

Phone (optional)

How did you find us? (optional)

🏫 Welcome, fellow educator!

I offer curriculum resources, practice materials, and study guides designed for AP CS teachers. Let me know what you're looking for — whether it's classroom materials, a guest speaker, or Teachers Pay Teachers resources.

Message (optional — leave blank if just subscribing)

✉

[email protected]

📚

Courses

AP CSA, CSP, & Cybersecurity

⏱

Response Time

Within 24 hours

Prefer email? Reach me directly at [email protected]