Maurice spent 1/2 of his money on lunch. He had 2.50 left. How much money did he start with?
1 answer:
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Answer:
D. a = 60 and b = 58.8
Step-by-step explanation:
Z-score:
In a set with mean and standard deviation
, the z-score of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
Z-score for data point a is 0.
This means that a is the mean, that is, a = 60.
The z-score for data point b is -0.4.
This means that b must be a value below the mean, that is, a value below 60.
The option that satisfies a = 60 and b < 60 is option D, which is the answer.
Answer:
a) 1/2
b) 250
Step-by-step explanation:
The start of the question doesn't matter entirely, although is interesting to read. What we are trying to do is find the value for such that
is maximized. Once we have that
, we can easily find the answer to part b.
Finding the value that maximizes is the same as finding the value that maximizes
, just on a smaller scale. So, we really want to maximize
. To do this, we will do a trick called completing the square.
.
Because there is a negative sign in front of the big squared term, combined with the fact that a square is always positive, means we need to find the value of such that the inner part of the square term is equal to
.
.
So, the answer to part a is .
We can then plug into the equation for p to find the answer to part b.
.
So, the answer to part b is .
And we're done!