A. Introduction
1 octal digit can be turned into 3 binary digits because 2^3=8.
000[0], 001[1], 010[2], 011[3], 100[4], 101[5], 110[6], 111[7]
1 hexadecimal digit can be mapped with 4 binary digits because 2^4=16
0000[0], 0001[1], 0010[2], 0011[3], 0100[4], 0101[5], 0110[6], 0111[7]
1000[8], 1001[9], 1010[A], 1011[B], 1100[C], 1101[D], 1110[E], 1111[F]
B. Conversion
From Octal / Hex to Binary: replace each digit the corresponding binary digits as above
From Binary to Octal / Hex: starting from the rightmost digit, turn every 3 or 4 digits into the corresponding Octal / Hex digit. Supply leading 0's as necessary.
From Octal to Hex: use Binary as a bridge.
C. Try:
1. A6
2. 532 (16) - 64 (16) = 4CE
3. A. 100010 B. 111010 C. 1011100 D. 1011 E. 10001100
Numbers with more 1 than 0: 111010, 1011100, 1011
4. 168C14
5. 10001001111
6. A