# Probability of Finger Ridge Counts

In the study of fingerprints, an important quantitative characteristic is the total ridge count for the 10 fingers of the individual. Suppose that the total ridge counts of individuals in a certain population are approximately normally distributed with a mean of 140 and a standard deviation of 50.

Find the probability that an individual picked at random from this population will have a ridge count of 200 or more.

In a population of 10,000 people how many would you expect to have a ridge count of 200 or more?

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#### Solution Preview

a) Denote the total ridge counts of individuals in a certain population by X. Then X is a random variable and approximately normally distributed with a mean of 140 and a standard deviation of 50, namely, ...

#### Solution Summary

In about 135 words, this solution provides a step by step explanation of how to approach this mathematical-based problem which requires the formulation of equations to solve for the ridge count in a specific population. All calculations are provided.