Number of cups of coffee = 9
Expressing to base 2
Bases of 2: 1, 2, 4, 8, 16, ...
Number lower than 9 and a base of 2 is 8.
8 goes into 9 once: 1 that is (9-(1)8=1)
Next is 4. 4 goes into the balance 0 times: 10 that is (1-(0)4=1)
Next is 2. 2 goes into balance 0 times: 100 that is (1-(0)2=1)
Final number is 1. 1 goes into balance once: 1001 that is (1-(1)1=0)
Therefore, 9 into base of 2 = 1001
