Answer:
6 paper towel rolls
Step-by-step explanation:
If she uses 1/2 of a paper towel roll each week and there are twelve weeks, divide the number of weeks by the number of paper towel rolls she uses.
Part A
Use the binomial probability distribution formula.
p = 0.54 = probability of getting a purple marble
n = 5 = sample size
x = 2 = number of purple we want to get

The
portion is from the nCr combination formula. The exclamation marks indicate a factorial.
Alternatively, you could use Pascal's Triangle for that portion.
<h3>Answer: 0.283831776</h3>
This decimal value is exact. Round it however you need to.
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Part B
To find the expected value, aka the mean, we multiply the sample size and probability of getting a purple marble on any single selection.
n*p = 5*0.54 = 2.7
<h3>Answer: 2.7</h3>
Well first turn 1/7 and 1/5 into decimals which would be .142857 and .2 Add those to 7 and 5 to get 7.143 (I rounded this to the nearest thousandth) and 5.2 Divide those and you get 1.374
X - 14 = 52
move - 14 for + 14
x = 52 + 14
x = 66