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In a fierce battle, not less than 70 percent of the soldiers lost one eye, not less than 75 percent lost one ear, not less than 80 percent lost one hand, and not less than 85 percent lost one leg. What is the minimal possible percentage of those who simultaneously lost one ear, one eye, one hand, and one leg? \(^{22}\)

Short Answer

Expert verified
The minimal percentage of soldiers who lost an eye, an ear, a hand, and a leg is 70%.

Step by step solution

01

Understand the Problem

We are given percentage conditions for soldiers losing different parts in a battle and need to determine the minimal percentage of soldiers who lost all the specified parts simultaneously.
02

Use Inclusion-Exclusion Principle

The problem can be approached using the Inclusion-Exclusion Principle to combine different percentage losses. We need to find the minimal overlap among those who lost an eye, an ear, a hand, and a leg.
03

Calculate Total Included Percent

Let's denote: - \( A = 70\% \) (lost an eye), - \( B = 75\% \) (lost an ear), - \( C = 80\% \) (lost a hand), - \( D = 85\% \) (lost a leg). Using Inclusion-Exclusion for four sets, the formula is: \[ |A \cap B \cap C \cap D| \geq |A| + |B| + |C| + |D| - |A \cup B \cup C \cup D| \]Since \(|A \cup B \cup C \cup D|\) is not greater than 100\%, it can be calculated by solving \(70 + 75 + 80 + 85 - 3x = 100\), where \(x\) is the overlap we solve for.
04

Simplify the Calculation

Simplify the equation from the previous step:\[ 70 + 75 + 80 + 85 - 3x = 100 \]Combine and solve for \(x\):\[ 310 - 3x = 100 \]\[ 3x = 210 \]\[ x = 70 \]
05

Conclusion for Solution

Thus, the minimal percentage of soldiers who lost all four parts is \( 70\% \). This represents the minimal overlap considering the least restrictive options, ensuring all conditions are met.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Understanding Percentage Conditions
Percentage conditions refer to specific constraints described in percentage terms. In our context, rather than precise numbers, we deal with a minimum percentage problem. For instance, if we say that 70% of soldiers lost an eye, it means 70% or more have suffered this loss. This stipulation is crucial as it sets a floor for our calculations rather than an exact number.
This approach is beneficial when identifying configurations that meet a series of minimum conditions. It emphasizes not only finding a solution that satisfies all individual requirements but also one that potentially represents an intersection — the focal point where all conditions overlap.
  • Percentage conditions are lower bounds, not fixed quantities.
  • These lower bounds form the basis for deduction and further probability scenarios.
  • Understanding these boundaries helps in applying more complex mathematical principles like the Inclusion-Exclusion Principle.
In practice, these percentage conditions guide the interpretation and manipulation of our data paths toward finding a commonality in probabilities such as in the battle problem we're analyzing.
Navigating Overlapping Sets
Overlapping sets arise when different groups share common elements. In mathematical problems, these are often represented as intersections of sets. When working with sets, especially under the Inclusion-Exclusion Principle, understanding overlaps is crucial.
Consider the overlapping conditions experienced by soldiers. One group lost an eye, another group lost an ear, yet another a hand, and a final group, a leg. The overlapping sets become significant because the goal is to determine who falls into all four categories simultaneously.
  • Each set overlaps with others, yielding subgroups with two or more losses.
  • The complexity grows with every additional condition set.
  • Through overlap analysis, we solve for the most critical intersection of all four conditions.
Overlapping sets affect how we calculate total overlaps because each condition interplays with the others, leading us to the potential minimum of the complete overlap — those soldiers who experienced all indicated losses.
Solving Probability Problems with Inclusion-Exclusion
In probability and set theory, the Inclusion-Exclusion Principle is a versatile tool for tackling complex problems involving multiple conditions. It is ideal for calculating the probability or percentage of total overlaps across several sets. This principle helps break down overlapping data into manageable parts.
In situations like the battle problem, Inclusion-Exclusion provides a framework to calculate how these overlap. By analyzing overlapping percentages, we identify the minimum percentage covering multiple conditions simultaneously.
  • Inclusion-Exclusion allows us to add up all individual percentages quickly.
  • Subsequently, it adjusts these percentages by subtracting out the unnecessary overlaps more than once.
  • This results in a clearer picture of how many meet all specified conditions.
Thus, through systematic application of Inclusion-Exclusion, we determine that not only are all the individual conditions met, but that it's possible to pinpoint a singular solution satisfying every set criteria. The exercise applies this principle to conclude that at least 70% of soldiers were part of all four targeted groups, striking a balance between probable inclusivity and exclusive overlap.

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Most popular questions from this chapter

The Labouchere system for roulette is played as follows. Write down a list of numbers, usually \(1,2,3,4 .\) Bet the sum of the first and last, \(1+4=5,\) on red. If you win, delete the first and last numbers from your list. If you lose, add the amount that you last bet to the end of your list. Then use the new list and bet the sum of the first and last numbers (if there is only one number, bet that amount). Continue until your list becomes empty. Show that, if this happens, you win the sum, \(1+2+3+4=10\), of your original list. Simulate this system and see if you do always stop and, hence, always win. If so, why is this not a foolproof gambling system?

The psychologist Tversky and his colleagues \(^{11}\) say that about four out of five people will answer (a) to the following question: A certain town is served by two hospitals. In the larger hospital about 45 babies are born each day, and in the smaller hospital 15 babies are born each day. Although the overall proportion of boys is about 50 percent, the actual proportion at either hospital may be more or less than 50 percent on any day. At the end of a year, which hospital will have the greater number of days on which more than 60 percent of the babies born were boys? (a) the large hospital (b) the small hospital (c) neither-the number of days will be about the same. Assume that the probability that a baby is a boy is .5 (actual estimates make this more like .513). Decide, by simulation, what the right answer is to the question. Can you suggest why so many people go wrong?

Give a possible sample space \(\Omega\) for each of the following experiments: (a) An election decides between two candidates \(\mathrm{A}\) and \(\mathrm{B}\). (b) A two-sided coin is tossed. (c) A student is asked for the month of the year and the day of the week on which her birthday falls. (d) A student is chosen at random from a class of ten students. (e) You receive a grade in this course.

A student must choose exactly two out of three electives: art, French, and mathematics. He chooses art with probability \(5 / 8,\) French with probability \(5 / 8,\) and art and French together with probability \(1 / 4 .\) What is the probability that he chooses mathematics? What is the probability that he chooses either art or French?

Consider the bet that all three dice will turn up sixes at least once in \(n\) rolls of three dice. Calculate \(f(n)\), the probability of at least one triple- six when three dice are rolled \(n\) times. Determine the smallest value of \(n\) necessary for a favorable bet that a triple-six will occur when three dice are rolled \(n\) times. (DeMoivre would say it should be about \(216 \log 2=149.7\) and so would answer 150 - see Exercise 1.2.17. Do you agree with him?)

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