probability quick question

if there are 15 beads in a bag, and 'three beads are selected at random from the bag and replaced', does this mean after each bead is picked it is replaced or after all three have been picked they're replaced? Hope that made sense? x

Can you please post the full question? That may help with understanding what it means.

There are 15 coloured beads in a bag; seven beads are red, three are blue and five are green. Three beads are selected at random from the bag and replaced. Find the probability that

a the first and second beads chosen are red and the third bead is blue or green,

b one red, one blue and one green bead are chosen.

Your first post said "not replaced" and this one just says "replaced". Can you confirm which one is what you're seeing?

'replaced' sorry!

I agree with the above poster : it's badly written but you can assume that it's replaced each time otherwise they wouldn't say it.

That’s not a very well written question! If that’s the whole thing, it probably means that the beads were replaced after each selection, or else there’d be no point in mentioning that they were replaced.

if there are 15 beads in a bag, and 'three beads are selected at random from the bag and replaced', does this mean after each bead is picked it is replaced or after all three have been picked they're replaced? Hope that made sense? x

There are 15 coloured beads in a bag; seven beads are red, three are blue and five are green. Three beads are selected at random from the bag and replaced. Find the probability that

a the first and second beads chosen are red and the third bead is blue or green,

b one red, one blue and one green bead are chosen.

I think they included the "replaced" part for section (b) or you might assume section (b)'s information is dependent on section A.

a:

(7 / 15) * (6/14) * (8/13) = 8 / 65

b:
Since all the beads were replaced, we can assume that everything is back to normal: 15 coloured beads now, 7 red, 3 blue 5 green

7 / 15 * 2 / 14 * 5 / 13 = 1 / 39

There are 15 coloured beads in a bag; seven beads are red, three are blue and five are green. Three beads are selected at random from the bag and replaced. Find the probability that

a the first and second beads chosen are red and the third bead is blue or green,

b one red, one blue and one green bead are chosen.

The version in the solution bank says "NOT replaced", which makes me think there's a typo in the version you're looking at.

And their subsequent solution implies "not replaced".