Question

this has me confused, please help solve..
a bag contains a total of 9 batteries, of which 5 are defective selecting 2 at random without replacement determine the probability that none of the batteries you select are good

Answer 1

combination problem

Answer 2

so would the answer be 5 /18

Answer 3

well, almost :)

Answer 4

can you evaluate this: 5C2/9C2

Answer 5

? ok where did i go wrong?

Answer 6

not completely.

Answer 7

none are good means both defective right? so take
\[\frac{5}{9}\times \frac{4}{8}\]

Answer 8

probability first one is defective is 5/9, probability second one is defective GIVEN that the first one was is 4/8 (clear yes? you have 8 batteries left of which 4 are defective)
AND means multiply them together

Answer 9

in fact i too get
\[\frac{5}{18}\] so unless i made a mistake (possible for sure) you are correct

Answer 10

i am sorry, @gensono2, i am a victum once again of my laziness, i had the answer as being 10/36, which means i did not simplify it 5/18.

Answer 11

you were correct

Answer 12

thank you. i do appreciate your help.. math and me just sometimes just dont get along (smiling)