A suitable probability calculator will tell you that probabilty is about 25.9%.
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The normalcdf function on this calculator gives an area between a lower and upper limit. If the upper limit is more than about 8 standard deviations above the mean, the 10th decimal place is unaffected. Since the standard deviation here is about 5, we need to have an upper limit that is about 40 above the mean of about 30. We have chosen 80 as a nice round number and to give a little more margin.
Answer:
<em>Riley has 72 tokens</em>
Step-by-step explanation:
<u>System of Equations </u>
We have two conditions for the tokens Riley and Erik have earned. Let's call x and y to the number of tokens of Riley and Erik respectively. The first condition states that
Solving for y
The second condition is that the ratio of the number of tokens that Riley had to the number of tokens that Erik has is 8 to 7. It's written as
Or equivalently
Replacing y from the first equation
Operating
Simplifying
Riley has 72 tokens