On top of a piece of paper right out 128 64 32 16 8 4 2 1
Underneath if all bits can be on (1) or off (0).
Then 11111111 (binary) added up equals 255 in decimal. I mean adding 128 +64+32+16+8+4+2+1 = 255.
255 minus 224 = 31 You cannot use the first address as that is always the network address and the last as that is the broadcast address. the range starts from 0 to 31 so 32 actual IP addresses but minus 2 equals 30 usuable for PCs/Hosts in that subnet.
You dont want all 255 addreses so in the last octect of 255.255.255.224 you mask with 1's and 0s what you do require.
You say you only need 10 host addresses so my mistake!!!!. The subnet mask that would provide 16 not 32 ip addresses is 255.255.255.240.
255 minus 240 = 15 Range 0 to 15 equals 16 IP addreses of which 14 are usable.
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