 # FAQ: Code Challenge: C++ Functions - Tenth Power

This community-built FAQ covers the “Tenth Power” exercise from the lesson “Code Challenge: C++ Functions”.

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This exercise can be found in the following Codecademy content:

## FAQs on the exercise Tenth Power

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``````
using namespace std;

class Student{
public:
float Marks;
char Name;
int Number;
Student(float marks[], int number , char name[]){
Number = number;
Name = name;
Marks = marks;
cout << "Hello: " << name << endl;
}
float calc_average(){
int m;
float sum=0, average;
for(m=0 ;m<Number; m++){
sum += Marks[m];
}
average =sum / 7;
return average;
}

};

int main (){
char name;
float marks;
int i, number;
char subjects  = {"Introduction to programming", "Programming Lab", "Discrete Math", "Introduction to Computer Systems", "Elements of Economics", "Communication Skills", "Physics for Computing Sysytems"};
cout << "Enter your name: ";
cin >> name;
for(i=0; i<7; i++){
cout << "Enter the marks for " << subjects[i] << ": ";
cin >> marks[i];
}

Student Gracio(marks, 7, name);
cout << "The average for your marks is: " << Gracio.calc_average() << "\n";

return 0;

}
``````

Could someone help please…It’s giving me the wrong average… Maybe you can help yourself: since it’s doing a bunch of stuff, how far does it get before things start being wrong? Since it’s a program that you are writing, you could add code in it that prints out everything that is being done.

1 Like

It’s all good until it comes to printing average…The function is actually returning a wrong average.

That’s not a black box either. You can look at what happens in it. It divides some sum by some length, doesn’t it? So is the sum right, is the length right? And if not, continue looking at whichever of them wasn’t right. #include
#include
// Define tenth_power() here:
double tenth_power(int num){
for (int i=0; i < 10; i++){
}
}
int main() {
std::cout << tenth_power(0) << “\n”;
std::cout << tenth_power(1) << “\n”;
std::cout << tenth_power(2) << “\n”;
}

this function works but it returns a double. The instructions don’t say the return needs to be an integer, only that the formal parameter should be. Is there any reason that the return ought to also be an integer?

1 Like

I am a little confused as where/when we learned the function “pow”. Did I miss something? Was it something I was supposed to know already? I don’t recall it in the notes.

1 Like

pow in C++

#include < iostream>
#include < c math>

// Define tenth_power() here:
int tenth_power(int num)
{
return pow(num, 10);
}

int main() {

std::cout << tenth_power(0) << “\n”;
std::cout << tenth_power(1) << “\n”;
std::cout << tenth_power(2) << “\n”;

}

Look at this snippet and see what is different.

``````#include <stdio.h>      /* printf */
#include <math.h>       /* pow */

int main ()
{
printf ("7 ^ 3 = %f\n", pow (7.0, 3.0) );
printf ("4.73 ^ 12 = %f\n", pow (4.73, 12.0) );
printf ("32.01 ^ 1.54 = %f\n", pow (32.01, 1.54) );
return 0;
}
``````

http://www.cplusplus.com/reference/cmath/pow/

You can use pow that we didn’t cover to this point or you can do like this.

``````int tenth_power(int num){
return (num * num * num * num * num * num * num * num * num * num);
}

int main() {

std::cout << tenth_power(0) << "\n";
std::cout << tenth_power(1) << "\n";
std::cout << tenth_power(2) << "\n";

}
``````

The reason we do

``````return pow(num, 10);
``````

Is to avoid doing things like

``````  return (num * num * num * num * num * num * num * num * num * num);
``````

What if it was raised to the power of 100?

Could use a loop.

1 Like