John left a $2 tip for the server when stopped at a diner. If this was 20% of his order total, how much was his order?
2 answers:
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The mean is and standard deviation is
. Then the variable
.
Use substitution , then the variable
.
The probability can be calculated in the following way:
for X=80, and
. From the diagram
.
Conclusion: if 188 students take the exam, then 188·0.84=157.92 (157) would receive a score above 80