Average of a NSArray and store value in a new NSArray

Average of a NSArray and store value in a new NSArray

i would like to have the average of my NSArray element and store them in a
new array in the following way.
NSArray* number;
NSMutableArray* Average;
[Average objectAtIndex:0]=[number objectAtIndex:0];
[Average objectAtIndex:1]=([number objectAtIndex:0] + [number
objectAtIndex:1])/2;
[Average objectAtIndex:2]=([number objectAtIndex:0] + [number
objectAtIndex:1] + [number objectAtIndex:2])/3;
i was thinking of doing it using 2 for loops
for (int i =0; i<[number count]; i++){
for (int j=0; j<i; j++){
temp+=[number objectAtIndex:j];
}
[Average addObject: temp/(i+1)];
}
can anyone help me with a more efficient way
thank you