Since we do not know the length, just assign something that represents the length which in this case is X. It says breadth is 3/5 of length which means it is 3X/5. Area is length times breadth and 3X^2/5 equals to 960. Solve for X and we got X equals to 40m. We know that X is length equal to 40. Now we do the same of breadth and we got breadth is 24. Sum all the lengths and breadths we have final answer of 128m