Algorithims & Complexity (Big O) and Sum count

Hi All

I need to calculate the number of times the sum is incremented with respect to the problem size n and give the Big O of the running time.

1.

int sum = 0;
int n = Some_Value;
for (int i=0; i<n*2; i++)
    sum++;
for (j=0; j<n; j++)
    sum++;

2.

int sum = 0;
int n = Some_Value;
for (int i=0; i<n/2; i++)
    for (j=0; j<n*n; j++)
        sum++;

3.

int sum = 0;
int n = Some_Value;
for (int i=0; i<n; i++)
    for (j=0; j<i; j++)
        sum++;

So would the following be correct ?

With regards to sum increment.

1. (n^2) + n
2. (n/2) x (n^2)
3. ? unsure on this one

With regards to the Big O

1. O(n^2) due to the outer loop O(n) and the inner loop is O(n).
2. O(n^3) due to the outer loop O(n) and the inner loop is O(n^2).
3. O(n) due to only O(n) comparisons in the outer loop.

Many Thanks
Steve