Assuming the sheet is a square
see diagram
the length will be 20-2x
the width will be 20-2x
and the height will be x
the volume will be (20-2x)(20-2x)(x)
The four outcomes are:
HH
HT
TH
TT
There are 4 outcomes that are possible. I've never seen anyone flip and edge, so that does not count.
The number of defective modems in the inventory is 20%⋅ 30 + 8%⋅ 50 = 10 (out of 80).
Note that the number of defectives in the inventory is fixed, i.e., we are not told that there
is 1
8 probability that a modem in the inventory is defective, but rather that exactly 1
8
of
all modems are defective. The probability that exactly two modems in a random sample
of five are defective is = 0.102