p124-125, p132-133

import java.util.*;
public class homework
{
    public static Scanner reader = new Scanner(System.in);
    public static void Q21() {
        int n, c = 0;
        for (int i = 1; i < 9; ++i) {
            System.out.print("Enter number: ");
            n = reader.nextInt();
            if (n % 2 == 0) c++;
        }
        System.out.println(c);
    }
    public static void Q22() {
        int c = 0;
        for (int i = 1; i < 301; ++i) {
            if (Math.sqrt(i) == (int)(Math.sqrt(i))) c++;
        }
        System.out.println(c);
    }
    public static void Q25() {
        System.out.print("Enter the number of people that atend the test: ");
        int n = reader.nextInt();
        int mistake, c = 0;
        for (int i = 0; i < n; ++i){
            System.out.print("Number of mistake in signs: ");
            mistake = reader.nextInt();
            if (mistake == 0){
                System.out.print("Number of mistake over all: ");
                mistake = reader.nextInt();
                if (mistake < 4) c++;
            }
        }
        System.out.println("Number of people that pass: " + c);
        System.out.println("Pass rate: " + c*100.0/n);
    }
    public static void Q27() {
        System.out.print("Enter number: ");
        int n = reader.nextInt();
        for (int i = 2; i < n; ++i) {
            if (n % i == 0) return;
        }
        System.out.println(n + " is a prime number");
    }
    public static void Q33() {
        int n, c = 0;
        for (int i = 0; i < 30; ++i) {
            System.out.print("Enter number: ");
            n = reader.nextInt();
            if (n > 9 && n < 100) c += n;
        }
        System.out.println("The sum of the even numbers: " + c);
    }
    public static void Q34() {
        System.out.print("Enter number: ");
        int n = reader.nextInt();
        int assembly = 1;
        for (int i = 1; i < n; ++i) {
            assembly *= i;
        }
        System.out.println("The assembly for" + n + "is: " + assembly);
    }
    public static void Q36() {
        System.out.println("-------------Q36-------------");
        System.out.print("Enter number: ");
        int n1 = reader.nextInt();
        System.out.print("Enter number: ");
        int n2 = reader.nextInt();
        int max = Math.max(n1,n2), min = Math.min(n1, n2);
        int sum = 0, mul = 1;
        for (int i = min; i < max; ++i) {
            sum += i; mul *= i;
        }
        System.out.println("The sum is: " + sum + ", and the product is: " + mul);
    }
    public static void Q38() {
        System.out.println("-------------Q38-------------");
        System.out.print("Enter base of exponent: ");
        int base = reader.nextInt();
        System.out.print("Enter exponent: ");
        int exp = reader.nextInt();
        for (int i = 1; i < exp; ++i) {
            base *= base;
        }
        System.out.println("The exponent is: " + base);
    }
    public static void Q39() {
        System.out.println("-------------Q39-------------");
        System.out.print("Enter number: ");
        int n = reader.nextInt();
        int c = 0;
        for (int i = 1; i < n; ++i) {
            if (n % i == 0) {
                c += i;
            }
        }
        if (c == n) {
            System.out.println(n + " is perfect number");
            for (int i = 1; i < n; ++i) {
                if (n % i == 0) { System.out.print(i + " + "); }
            }
        }
    }
        public static void main(String[] args)
    {
        Q21();Q22();Q25();Q27();Q33();Q34();Q36();Q38();Q39();
    }
}