There are blue, red, and green marbles in a jar. There are 7 blue marbles in the jar. The probability of getting a blue marble is 1/6 and the probability of green is 5/21.

Question

a. How many marbles are there in the jar?

b. How many green marbles are there in the jar?

c. How many red marbles are there in the jar?

Answer 1

Hi Anika,

Let us define the following variables:

n(B) = number of blue marbles in the jar

n(R) = number of red marbles in the jar

n(G) = number of green marbles in the jar

N = total number of marbles in the jar

a) P(B) = n(B)/N = 7/N

we are given P(B) = 1/6

so 7/N = 1/6

=> N = 42

so there are 42 marbles in the jar.

b)

P(G) = n(G)/N = n(G)/42

we are given P(G) = 5/21

so n(G)/42 = 5/21

=> n(G) = 10

so there are 10 green marbles in the jar.

c)

n(R) = N - n(B) - n(G)

=> n(G) = 42 - 7 - 10 = 25

So there are 25 red marbles in the jar.

Hope this helps!