The total required RAM is 2048 Bytes that is 2048*8 bits ..
Now we have a chip of 512 * 8 bits that is ..it has 512 entries with entry of 8 bits each ..
While as per our need we want RAM such that it has 2048 slots each of 8 bits ..
so total CHIPS needed= 2048*8 / 512*8 = 4 Chips