## >_ Problem

Modify the program you wrote in Programming Challenge 20 (Pizza Pi) so that it reports the number of pizzas you need to buy for a party if each person attending is expected to eat an average of four slices. The program should ask the user for the number of people who will be at the party and for the diameter of the pizzas to be ordered. It should then calculate and display the number of pizzas to purchase.

## >_ Solution

```
#include <iostream>
#include <iomanip> // setprecision(3) .000
#include <cmath> // pow(6, 3) == 6^3
using namespace std;
int main()
{
// Constants
const float SLICE_AREA_SIZE = 14.125,
PI = 3.14159;
const int TWO = 2,
FOUR = 4;
// Variables
float d,
r,
Area,
num_of_slices,
slices_needed,
num_of_pizzas;
int num_of_people;
// Ask the user for the number of people who will be at the party
cout << "\nWhat is the number of people who will be at the party? ";
cin >> num_of_people;
// Ask the user for the diameter of the pizza in inches.
cout << "What is the diameter of the pizza in inches? ";
cin >> d;
// Calculate the # of slices
// Num Slices needed
slices_needed = num_of_people * FOUR;
// Calculate Radius
r = d / TWO;
// Calculate Area
Area = PI * pow(r, TWO);
// Num Slices per pizza
num_of_slices = Area / SLICE_AREA_SIZE;
// Num pizzas needed
num_of_pizzas = slices_needed / num_of_slices;
// Display a message telling the number of slices.
cout << setprecision(1) << fixed;
cout << "Number of people = ";
cout << num_of_people << endl;
cout << "Number of slices needed = ";
cout << slices_needed << endl;
cout << "Number of slices per Pizza = ";
cout << num_of_slices << endl;
cout << "Number of pizzas to order = ";
cout << num_of_pizzas << endl;
cout << endl;
// Terminate Program
return 0;
}
```

## >_Get The Book!

## >_ Video Walk Through

This video includes a step by step process of how I solve programming challenge #21.

## >_That’s it!

Thank you for taking interest what I do! I hope it was helpful for you as much as it helped me along my journey in learning to code!

## >_ Also Check Out:

Category: Starting Out With C++ | Chapter 3 | Programming Challenge Solutions