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Question

If '+' and '-' are interchanged and also the numbers 8 and 6 change places, which of the

following options is correct?

The correct answer is

12 + 6 - 8 = 10

Understanding the Operator and Number Interchanges

The question asks us to apply specific rules of interchange to mathematical expressions and then determine which of the given options remains correct after these changes. The rules for interchange are:

  • The operator '+' is interchanged with the operator '-'.
  • The number '8' is interchanged with the number '6'.

This means wherever a '+' appears, it becomes '-', and wherever a '-' appears, it becomes '+'. Similarly, wherever '8' appears, it becomes '6', and wherever '6' appears, it becomes '8'. Other numbers and operators remain unchanged.

Applying Interchanges to Each Option

Let's go through each given option and apply the specified interchanges to the expression on the left side of the equality sign. We will then evaluate the new expression and compare it to the original result on the right side.

Option 1: Evaluating 6 - 8 - 8 + 8 = 0

  • Original expression: $6 - 8 - 8 + 8$
  • Applying interchanges: '6' becomes '8', '-' becomes '+', '8' becomes '6', '+' becomes '-'.
  • Modified expression: $8 + 6 + 6 - 6$
  • Evaluating the modified expression: $8 + 6 + 6 - 6 = 14 + 6 - 6 = 20 - 6 = 14$
  • Original result: $0$
  • Comparison: $14 \neq 0$. This option is not correct after the interchanges.

Option 2: Evaluating 12 + 8 - 6 = 2

  • Original expression: $12 + 8 - 6$
  • Applying interchanges: '+' becomes '-', '8' becomes '6', '-' becomes '+', '6' becomes '8'. The number '12' remains unchanged.
  • Modified expression: $12 - 6 + 8$
  • Evaluating the modified expression: $12 - 6 + 8 = 6 + 8 = 14$
  • Original result: $2$
  • Comparison: $14 \neq 2$. This option is not correct after the interchanges.

Option 3: Evaluating 12 + 6 - 8 = 10

  • Original expression: $12 + 6 - 8$
  • Applying interchanges: '+' becomes '-', '6' becomes '8', '-' becomes '+', '8' becomes '6'. The number '12' remains unchanged.
  • Modified expression: $12 - 8 + 6$
  • Evaluating the modified expression: $12 - 8 + 6 = 4 + 6 = 10$
  • Original result: $10$
  • Comparison: $10 = 10$. This option is correct after the interchanges.

Option 4: Evaluating 6 - 4 + 8 - 8 = 6

  • Original expression: $6 - 4 + 8 - 8$
  • Applying interchanges: '6' becomes '8', '-' becomes '+', '4' remains unchanged, '+' becomes '-', '8' becomes '6', '-' becomes '+', '8' becomes '6'.
  • Modified expression: $8 + 4 - 6 + 6$
  • Evaluating the modified expression: $8 + 4 - 6 + 6 = 12 - 6 + 6 = 6 + 6 = 12$
  • Original result: $6$
  • Comparison: $12 \neq 6$. This option is not correct after the interchanges.

Summary of Evaluation

Let's summarize the results in a table for clarity:

Original Option Interchanges Applied ( '+' $\leftrightarrow$ '-', '8' $\leftrightarrow$ '6' ) Modified Expression Evaluation Original Result Correct?
$6 - 8 - 8 + 8 = 0$ $8 + 6 + 6 - 6$ $14$ $0$ No
$12 + 8 - 6 = 2$ $12 - 6 + 8$ $14$ $2$ No
$12 + 6 - 8 = 10$ $12 - 8 + 6$ $10$ $10$ Yes
$6 - 4 + 8 - 8 = 6$ $8 + 4 - 6 + 6$ $12$ $6$ No

Based on the evaluations, only Option 3 results in the original equality holding true after applying the given interchanges.

Conclusion on Interchanging Operators and Numbers

When operators and numbers are interchanged according to the specific rules provided in the question, we must carefully substitute each instance of the specified operators and numbers in the given expressions. After performing these substitutions, we evaluate the new mathematical expression. The option for which the evaluated result matches the original result stated in the option is the correct answer.

Revision Table: Key Concepts

Concept Explanation Importance in this Problem
Interchange Rules Specific rules defining which symbols/numbers swap places or meanings. Crucial for correctly transforming the expressions.
Order of Operations Rules like PEMDAS/BODMAS for evaluating expressions (although in this problem, simple addition/subtraction from left to right is sufficient). Ensures correct calculation of the modified expression.
Equality The state where the value of the expression on the left side equals the value on the right side. The condition that must remain true after interchanges for an option to be correct.

Additional Information: Logical Reasoning with Symbols

Problems involving interchanging symbols or numbers are common in logical reasoning or mathematical puzzle sections of exams. They test your ability to follow instructions precisely and apply transformations consistently. Here are some related concepts:

  • Symbol Substitution: Replacing one symbol or character with another based on a given rule.
  • Code-Breaking: Similar to substitution, where symbols represent other values or operations, and you need to decode the message or expression.
  • Pattern Recognition: Sometimes the interchanges might follow a pattern rather than a simple one-to-one swap.
  • Mathematical Operations: A strong understanding of basic arithmetic operations (addition, subtraction, multiplication, division) and their order is necessary to evaluate the transformed expressions correctly.

In this specific problem, the interchange is straightforward: '+' and '-' swap, and '8' and '6' swap. The key is systematic application of these rules to each part of the equation and then correctly performing the arithmetic.

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Important Questions from Logical Puzzle

  1. Which two numbers should be interchanged to make the given equation correct?

    9 + 7 × 5 – 18 ÷ 2 = 3 × 4 – 10 + 45 ÷ 5
  2. Select the correct combination of mathematical signs that can sequentially replace the * signs and balance the equation.

    60 * 2 * 3 * 6 * 5 * 43

  3. Which of the following interchange of numbers and mathematical signs would make the given equation correct?

    30 ÷ 6 × 4 + 15 - 35 = 25

  4. Which two signs need to be interchanged to make the following equation correct?

    23 + 84 ÷ 14 × 8 − 3 = 5

  5. Select the correct combination of mathematical signs that can sequentially replace the * signs and make the equation correct.

    68 * 138* 23 * 54 * 20

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