For every bit you can record two possible data and the amount will increase by rate 2^x where x is the number of bit. To answer this question, you need to know what is the least amount 2^x that will be enough to record 1000 possibilities.
To do this, it is easier to divide the number with 32 for 5 bits(2^5=32), then divide it with 2 for 1 bit until it less than 1. The calculation would be: 1000/32= 31.25 /32= 0.976.
The answer would be 5 bit+ 5bit= 10 bit. (2^10= 1024)
