help with the math in my C++ program

[bobsakamano]

Hi, i am wrighting a program that calcultes gas milage based on how much the driver uses the city/highway. here is what i have so far :

#include <iostream>

using namespace std;

int main(){
double tankSize, city, highway;
int cost;
int percent;

cout << "Enter the size of the gas tank of the car in gallons: ";
cin >> tankSize;

cout <<"Enter the MPG you get in the city: ";
cin >> city;

cout <<"Enter the MPG you get in the highway: "; 
cin >> highway;	

cout << "What percentage do you travel on the highway? ";
cin >> percent;





return 0;
}

i need to determine the amount of miles that can be traveled for a single tank of gas.

[D80DSL3A]

Look up "interpolation" for the method here.

I'll use a double for percent instead of an int.
Assuming percent is entered as a value between 0 and 100 then:
actualMPG = highway*percent/100.0 + city*(1 - percent/100.0);