/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 158 At an election, a voter may vote... [FREE SOLUTION] | 91Ó°ÊÓ

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At an election, a voter may vote for any number of candidates, not greater than the number to be elected. There are 10 candidates and 4 are of be elected. If a voter votes for at least one candidate, then the number of ways in which he can vote is (A) 5040 (B) 6210 (C) 385 (D) 1110

Short Answer

Expert verified
385 ways, which corresponds to option (C).

Step by step solution

01

Understanding the Problem

We need to determine the number of ways a voter can vote for up to 4 candidates out of 10, ensuring the voter votes for at least one candidate.
02

Calculate Total Possible Ways Without Restriction

First, we find the total number of ways to select any number of candidates (from 0 to 4) from the 10 available candidates. The total number of subsets possible is given by the sum of combinations: \( \sum_{k=0}^{4} \binom{10}{k} \).
03

Calculate Individual Combinations

Now, calculate each of these combinations: - \( \binom{10}{0} = 1 \)- \( \binom{10}{1} = 10 \)- \( \binom{10}{2} = 45 \)- \( \binom{10}{3} = 120 \)- \( \binom{10}{4} = 210 \)
04

Sum the Combinations

Add up the values calculated for each number of candidates: \[ 1 + 10 + 45 + 120 + 210 = 386 \]
05

Subtract the Invalid Case

The case where the voter does not vote for any candidate (0 candidates) is invalid because the problem states the voter votes for at least one. Thus, we subtract \( \binom{10}{0} = 1 \): \[ 386 - 1 = 385 \]
06

Conclusion and Correct Option

The correct number of ways in which the voter can cast votes for at least one candidate is 385. The correct option is (C) 385.

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Key Concepts

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

Election mathematics
Election mathematics is a crucial area of mathematics that deals with counting and arrangements related to elections. Understanding how voters can choose candidates under specific rules is vital in election systems. In this context, it assesses different conditions like eligibility, number of candidates, and voting methods that can alter the outcome.

In voting scenarios where multiple candidates can be chosen, election mathematics often utilizes combinatorial techniques. These techniques help determine the number of possible ways voters can express their preferences. This is essential for understanding the complexity of elections and ensuring fair results.

When voters can select from a set number of candidates, tools like combinations and permutations are employed. These help in counting the number of ways to create valid choices or preferences. For instance, understanding how many sets of candidates a voter can select is key to predicting election outcomes and ensuring democratic processes.
Combination selection
Combination selection is at the core of solving problems where the order of selection does not matter. In elections, voters might need to choose a subset of candidates where the sequence of choice is irrelevant, which is where combinations come into play.

Mathematically, a combination is a selection of items from a larger set, where the sequence does not matter. The formula to calculate combinations is given by:
  • \( \binom{n}{r} = \frac{n!}{r!(n-r)!} \)
Here, \( n \) is the total number of items to choose from, and \( r \) is the number of items to be selected.

In the context of our exercise, combination selection helps voters choose candidates without worrying about the order. Voters select different combinations to vote within the limits prescribed, ensuring every voter choice reflects valid, comparable outcomes. Understanding combination selection ensures that the election math is applied correctly, allowing fair and equitable elections.
Voting permutations
Voting permutations differ from combinations by considering the order of selection. However, in many election styles, particularly when choosing candidates to elect, the order may not matter.

Permutations become relevant when voters have to rank preferences or when positions differ in significance. A permutation of a set is any arrangement of the members of the set, taking their order into account. The formula for permutations is:
  • \( P(n, r) = \frac{n!}{(n-r)!} \)
This arrangement includes various formats, but when voters select candidates with no emphasis on who's chosen first, permutations might give way to combinations.

In our example exercise, since voting directions indicate no preference on order, combinations are used. Should the rank of choices matter, permutations would then be the appropriate method, demonstrating how both mathematical concepts are crucial in understanding voting scenarios.

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