Question

Molly's mugs has the following in stock: (below here is a table)


Small medium large total
Plastic 12 8 5 25
Metal 6 14 10 30
Ceramic 20 28 25 73
Total 38 50 40 128


Find the probabilities if one mug is randomly selected.
a) The probability that the mug is metal.
b) The probability that it is a small, ceramic mug.
c) The probability that the mug is metal or large.
d) The probability that it is not a medium mug.
e) The probability that it is ceramic, given that it is large.
f) The probability that it is small, given that it is a plastic mug.

My answers:
a) P(Metal) = 30/128
b) P (Small∩Ceramic) = 20/128
c) P (Metal U Large) = P (Metal) + P (Large) - P (Metal∩Large)
= 30/128 + 40/128 - 10/128 = 15/32
d) Complement. So i did 1-p(medium)= 1- 50/128= 39/64
e) P (Ceramic l Large)= P (C∩L)/ P(L) = 25/128 divided by 40/128 =5/8
f) P( Small l Plastic) = P(S∩P)/P(P) = 12/128 divided by 38/128 = 6/19

Answer 1

looks good

Answer 2

I was wondering because my professor gave us these answers:
a) 30/128
b) 6/128
c) 70/128
d) 78/128
e) 25/40
f)12/25

Answer 3

I looked at you procedure, not the actual arithmetic

A closer look at the last one shows that you had P(P) = 38/128
should have been 25/128, which gives the prof's answer of 12/25

check that your chart entries are correct

I did the others independent of you answers and still agree with a) - e)