Decoder

Question 1
 
A
xz+x’z’
B
xz’+x’z
C
x’y’+yz
D
xy+y’z’
       Digital Logic Design        Decoder       Gate 2008-IT
Question 1 Explanation: 
Question 2
How many 3-to-8 line decoders with an enable input are needed to construct a 6-to-64 line decoder without using any other logic gates?
A
7
B
8
C
9
D
10
       Digital Logic Design        Decoder       Gate-2007
Question 2 Explanation: 
Each 3-to-8 lines decoder has 8 output lines.
Number of 3-to-8 decoders needed for 64 output lines of 6-to-64 Decoder is 8.
One more 3-to-8 lines Decoder is needed to select one of the eight 3-to-8 Decoders.
So 8+1= 9 decoders are needed.
There are 2 questions to complete.