How many number of 2:4 line decoders are required for implementing 4:16 line decoder?

To implement a 4:16 line decoder, we need 4 of the 2:4 line decoders. Here's the step by step process:

1. First, understand that a 2:4 line decoder has 2 input lines and 4 output lines. It decodes the input into one of the 4 output lines.

2. A 4:16 line decoder, on the other hand, has 4 input lines and 16 output lines. It decodes the input into one of the 16 output lines.

3. To implement a 4:16 line decoder using 2:4 line decoders, we need to increase the number of output lines from 4 to 16. This can be done by using 4 of the 2:4 line decoders.

4. The first 2:4 line decoder is used to decode the first 2 input lines. The output of this decoder is used to enable one of the other three 2:4 line decoders.

5. The remaining 2 input lines are connected to the input of the other three 2:4 line decoders. This way, when the first decoder enables one of the other decoders, the input is decoded into one of the 16 output lines.

So, in conclusion, we need 4 of the 2:4 line decoders to implement a 4:16 line decoder.