Write a program to read in two consumer price indexes and print out the inflation rate. 1. Start with the student starter code and follow the instructions in the code.
2. Instructions to complete are tagged in comments like the ones below. They will always begin with // TODO. // TODO #1: declare two float variables for the old consumer price index (cpi) and the new cpi // TODO #2: Read in two float values for the cpi and store them in the variables
// TODO #3: call the function InflationRate with the two cpis // TODO #4: print the results
3. Once you have this program working, submit for credit.
4. Advance to the next lab InflationRate Part2.

Here is the C++ program:

#include<iostream>  //to use input output functions

#include<cmath>  //to use math functions

using namespace std;  //to identify objects cin cout

double InflationRate(float oldCPI,float newCPI);  //function prototype

int main() {  //start of main function

  float oldCPI,newCPI,rate;  //declares two float variables for the old and consumer price indices

  char choice;  //stores user choice to continue

  double sum=0.0;  // computes the sum of inflation rates

  int count = 0;  //to count the number of inflation rates computed

  double average = 0.0;  //to compute the average inflation rate

  do   {  //this loop continues to execute and ask user to enter cpis

  cout << "Enter the old and new consumer price indices: ";  //prompts user to enter new and old cpi

  cin>>oldCPI>>newCPI;  // Read in two float values for the cpi

  rate = InflationRate(oldCPI,newCPI);  //call the function InflationRate with the two cpis

  cout << "Inflation rate is: "<< rate<< endl;  //displays the result

  sum = sum + rate;  //computes sum of inflation rates

  count++;  //counts number of computed inflation rates

  cout<<"Try again? (Y or y): ";  //prompts if user wants to continue

  cin>>choice;  //reads choice of user y or Y

  }while((choice=='Y')||(choice=='y'));  //the loop continues to repeat as long as user enters small or capital y

  average = sum/count;  //computes the average inflation rate

  cout<<"Average rate is: "<<average;}  //displays the average inflation rate

double InflationRate(float oldCPI,float newCPI){  // function that takes two arguments oldCPI and new CPI and computes the inflation rate

   return (newCPI - oldCPI) / oldCPI * 100;} //formula to compute inflation rate

Explanation:

1.        

/*This program computes the inflation rate using two consumer price indexes. It takes as parameters, the previous price index and current price index and computes inflation rate by the formula:

(newCPI- oldCPI) / oldCPI and multiply the result by 100 */

#include <iostream>  //to use input output functions

using namespace std;   //to identify objects cin cout

2.

float oldCPI, newCPI; //declare two float variables for old and new consumer price index

cout << "Enter the old and new consumer price indices: ";  //prompts user to enter values for old and new cpi

cin>>oldCPI>>newCPI; //read in two float values for the cpi and store them in the variables oldCPI and newCPI

double result = InflationRate(oldCPI,newCPI); //call the function InflationRate with the two cpis

cout << "Inflation rate is:  " << result<< endl; //prints the result

3. and 4.

The complete program is given in the Answer section

For example if user enters 238.343 as old cpi and 238.250 as new cpi then the program works as follows:

oldCPI =238.343

newCPI = 238.250

Now the function InflationRate is called by passing these two parameter and this function returns :

   return (newCPI - oldCPI) / oldCPI * 100;}

this becomes

(newCPI - oldCPI) / oldCPI * 100

(238.250 - 238.343) / 238.343  * 100

-0.093/238.343  * 100

- 0.00039 * 100

= -0.039 0204

Hence

result = -0.039 0204

Next, sum = sum + rate; statement computes the sum as:

sum = 0.0 + (-0.039 0204)

sum = -0.039 0204

count++ increases the count by 1

count = 1

Next user is asked if he/she wants to continues. If user presses y or Y then user is asked again to enter values for new and old cpi. Suppose user enters the following values:  

oldCPI =238.250

newCPI = 237.852

Now the function InflationRate is called by passing these two parameter and this function returns :

   return (237.852- 238.250) / 238.250* 100;}

this becomes

(newCPI - oldCPI) / oldCPI * 100

(237.852- 238.250) / 238.250* 100

−0.398/238.250* 100

- 0.001670491 * 100

= -0.167049

Hence

result = -0.167049

Next, sum = sum + rate; statement computes the sum as:

sum =  -0.039 0204 + (-0.167049)

sum = -0.206069

count++ increases the count by 1

count = 2

Now lets say the user enters n or any other key when asked if user wants to continue. So the loop breaks and program moves to the statement:

average = sum/count;

This becomes:

average = -0.206069/2

average = −0.103034

Hence

Average rate is: −0.103034