Question

A bag contains 7 blue marbles, 8 green marbles, 15 red marbles, and 10 yellow marbles. Find the probability of randomly drawing without replacement, a blue marble and then a red.

a. 7/160 or about 0.0438
b. 21/320 or about 0.0656
c. 7/104 or about 0.0673
d. 15/66 or about 0.2273

Answer 1

i think its b) 21/320

Answer 2

I actually get 21/319

Answer 3

21/312 I mean :/

Answer 4

are you sure? when you divide 1600 by 5 you get 320 right?

Answer 5

it says "without replacement" so the way I see it (and I can be wrong) the first drawing is 7/40 and the second is 15/39 (because on the second drawing there are only 39 marbles in the bag)

either way that is very close to b)

Answer 6

hmm youre right but its still close to b

Answer 7

oh yeah, that's a choice
I forgot how to simplify :)
no, I'm pretty sure I'm right

Answer 8

you can simplify my answer, and it does not simplify to b)

Answer 9

right but i think you should still choose be since it is closest to 21/319

Answer 10

no, that was a typo
my answer is \[\frac7{40}\times\frac{15}{39}\]

Answer 11

simplify...

Answer 12

does that reasoning make sense to you?

Answer 13

yes so if you simplfy you get 105/1560 then if you divide by 5 you get 21/319

Answer 14

no, check your arithmetic
the whole point is that there are fewer marbles in the bag on the second drawing

Answer 15

hmm but isnt the question asking the probablity of picking a red then blue with out replacement??

Answer 16

right, no replacement means 40 marbles in the bag the first time, and 39 in the bag the second
make sense?

Answer 17

if there was replacement that would mean we put the first blue marble back, and there would be 40 marbles again in the bag for the second drawing
without putting that blue marble we pulled out back the bag is 1 marble short; 39

Answer 18

right

Answer 19

so now that you see where the fractions come from, just compute\[\frac7{40}\times\frac{15}{39}\]and be careful with your simplification