Question

How many 1-of-16 decoders are required for decoding a 7-bit binary number?

Answer 1

7-bit binary number” has 128 possible numbers - outputs, so you need minimum 9 (128/16+1) 1-of-16 decoders. Always decoders have “enable” port, which enables outputs. One decoder is used for selecting which decoder between 8 others is active