Question

Cherise has a bag of marbles for her little sister. It contains 10 orange marbles, 7 yellow marbles, and 3 green marbles. She drops the bag and 3 marbles roll out. What is the probability that all 3 marbles are yellow?

a. 343/8000

b. 21/800

c. 7/228

d. 3/20

The weights of rats in a city are normally distributed with a mean of 2.5 pounds and a standard deviation of 0.5 pounds.

About what percent of the rats in the city weigh between 2.0 pounds and 3.0 pounds?

a. 81.5%

b. 68%

c. 47.5%

d. 34%

Answer 1

The probability that all marbles are yellow is
(7/20) (7/20) (7/20) = 343/8000

We are given
x = 2 and 3
u = 2.5
s = 0.5

Getting the z score
z = (2 - 2.5) / 0.5 and (3 - 2.5)/ 0.5
z = -1 and 1
The percentage is 
1 - 0.1557 = 81.5%