Uses Of Computers

QUESTION 1.

Write a program to solve the following equation with values of n & c being entered by the user

(n! * (n-c)!) / c!

import java.io.*;

class Calc

{ //class begins

public void main()throws IOException

{ //main() begins

BufferedReader ob=new BufferedReader(new InputStreamReader(System.in));

System.out.println("Enter the value of n.");

int n=Integer.parseInt(ob.readLine());

System.out.println("Enter the value of c.");

int c=Integer.parseInt(ob.readLine());

int x,y,z;

x=factorial(n);

y=factorial(c);

z=factorial(n-c);

System.out.print("nThe value of (n!*(n-c)!)/c! is : "+((double)(x*z)/y)); /*printing the answer

along with a message*/

} //main() ends

public int factorial(int a)

{ //factorial() begins

int i,f=1;

for(i=1; i<=a; i++)

{

f=f*i;

}

return f;

} //factorial() ends

} //class ends

VARIABLE DESCRIPTION

NAME

TYPE

PURPOSE

n

int

Value entered by user

c

Int

Value entered by user

x

Int

To store factorial of n

y

int

To store factorial of c

z

Int

To store factorial of (n-c)

i

Int

Index variable of the loop to find factorials

f

Int

To store factorial.

OUTPUT

Enter the value of n.

10

Enter the value of c.

19

The value of (n!*(n-c)!)/c! is : 0.03309688807531381

QUESTION 2.

Write a program that will display all the prime palindrome numbers with a suitable message.

class Palindromes

{ // class begins

public void main()

{ // main() begins

int i,j,rem,rev,num; //declaring the variables used

boolean x;

System.out.println("Prime Palindrome numbers from 10 to 1000 are :");

for(i=10; i<=1000; i++)

{ // outer for loop begins

rev=0;

num=i;

while(num!=0) // loop to find reverse of the numbers

{

rem=num%10;

rev=rev*10+rem;

num=num/10;

}

if(rev==i)

{ //condition to check if the palindrome is prime or not

x=isPrime(i);

if(x==true)

System.out.print(i+" ");

}

} // outer for loop ends

} // main() ends

public boolean isPrime(int a)

...