Question

A bag contains 50 marbles, 10 of which are blue, 8 are red, 20 are green, and 12 are purple. Marcie takes a marble out of the bag, records the color, and returns it to the bag. How many red marbles should she expect after 500 trials?

Answer 1

@tkhunny

Answer 2

@phi

Answer 3

are there any answer choices?

Answer 4

80

100

120

200

Answer 5

not completely sure but i think its 120

Answer 6

Do you know how to find the probability of picking a red marble?

Answer 7

no

Answer 8

Probability is # of "good" choices / total number

in this case # of red / total number of marbles
what do you get ?

Answer 9

50 /8 6.25 but 500/8 62.5

Answer 10

the ratio of 50 to 8 remains constant: 50n to 8n, such that 50n=500, what is n?

Answer 11

10 of which are blue, 8 are red, 20 are green, and 12 are purple

Checking: 10 + 8 + 20 + 12 = 50 -- Good
Theoretical Ratios: Blue 10/50 = 20%, Red 8/50 = 16%, Green 20/50 = 40%, Purple 12/50 = 24%

Checking: 20 + 16 + 40 + 24 = 100 -- Good!

See how that works?

Mind you, this is WITH REPLACEMENT. The probabilities and ratios are constant. If you start throwing them away, rather than putting them back, it's a different world.