practice-midterm-answers.md

Practice Midterm Answers

Week 5

1. Expressions, 10 points.

   Expression	Value
   13 + 2 * 5 / 3	16
   2.5 * 2 * 5 / 10 + 1.5	4.0
   85 % 10 + 4 % 10 - 17 % 3	7
   2 + 3 + "." + (3 + 4) + 2 * 3	"5.76"
   482 / 10 / 5 / 2.0 * 2 + 14 / 5	11.0

2. Parameter Mystery, 12 points.

   skip likes to drive with george
   george likes to work with drive
   george likes to skip with mary
   john likes to dance with mary
   

3. If/Else Simulation, 12 points.

   Method Call	Output Produced
   ifElseMystery(14, 14);	14 13
   ifElseMystery(4, 5);	7 5
   ifElseMystery(10, 5);	12 10
   ifElseMystery(2, 8);	3 8

4. While Loop Simulation, 12 points.

   Method Call	Output Produced
   mystery(8);	1 8
   mystery(32);	2 5
   mystery(184);	3 13
   mystery(8239);	4 22

5. Assertions, 15 points.

   	x > y	z == 0	x == y
   Point A	S	A	S
   Point B	S	S	N
   Point C	A	N	N
   Point D	N	N	N
   Point E	N	S	A

6. One possible solution appears below. Your solution may be different and still correct, there are many ways to solve these problems.

   public static void giveProblems(Scanner console, int numProblems) {
       Random r = new Random();
       int numRight = 0;
       for (int i = 1; i <= numProblems; i++) {
           int x = r.nextInt(12) + 1;
           int y = r.nextInt(12) + 1;
           System.out.print(x + " * " + y + " =? ");
           int answer = x * y;
           int response = console.nextInt();
           if (response == answer) {
               System.out.println("correct");
               numRight++;
           } else {
               System.out.println("incorrect...the answer was " + answer);
           }
       }
       System.out.println(numRight + " of " + numProblems + " correct");
   }

7. One possible solution appears below. Your solution may be different and still correct, there are many ways to solve these problems.

   public static int printSequenceTo(double value) {
       double sum = 0.5;
       System.out.print("1/2");
       int n = 1;
       while (sum < value) {
           n++;
           System.out.print(" + " + n + "/" + (n + 1));
           sum = sum + (double) n / (n + 1);
       }
       System.out.println(" = " + sum);
       return n;
   }

8. One possible solution appears below. Your solution may be different and still correct, there are many ways to solve these problems.

   public static int weave(int x, int y) {
       int result = 0;
       int multiplier = 1;
       while (x != 0 || y != 0) {
           result = result + multiplier * (x % 10 * 10 + y % 10);
           multiplier = multiplier * 100;
           x = x / 10;
           y = y / 10;
       }
       return result;
   }