as it is a upper triangular matrix u need not store the zero's...so it is just like accessing the array[45][47]....we can assume the array as array[50][50],....so the 51st element in first row will have address of 5000....now second row will have one zero no need to store we will get the last element address by adding 4900 to it...so on proceeding like this uptil array[44][50]...the lasst element will be given by adding (5000-4400=600)...so adding these all we get 5000+4900+...+600.=126000...but we want a[45][47] so in the 45th row u have 46 zeros so u need to add 200 to it 126000+200=126200... iam getting this 126200