There are are $100*100 = 10,000$ elements in the array.
Page size $= 800$ bytes, int size $= 4$ Bytes, hence each page can contain $800/4 = 200$ int elements
Array is accessed column wise and array is stored in the memory row wise. for example $A[0][0], A[1][0], A[2][0]$ an so on elements are accessed.
A single memory page can contain 200 elements (or) 2 rows on single access to memory
1. From $A[0][0] to A[0][99]$ and from $A[1][0] to A[1][99]$
2. From $A[2][0] to A[2][99]$ and from $A[3][0] to A[3][99]$, and so on..
It means every first access is miss and every second access is hit, so miss rate $= 50%$, hit rate$=50%$.
There are $10,000$ elements in the array, hence there will be $5000$ miss.