Answer:
1 13/64
Step-by-step explanation:
The depth of the hole is the height of the block less the remaining material below the hole:
depth = 1 3/8 +1 15/16 - 3/8 = (1 3/8 -3/8) +1 15/16 = 2 15/16
We want to find the difference between this depth and the depth of the hole already drilled:
2 15/16 -1 47/64 = 2 60/64 -1 47/64
= (2 -1) +(60 -47)/64 = 1 13/64
The hole must be drilled 1 13/64 deeper to match the drawing.