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Question

The second number in the given number pairs is obtained by performing certain mathematical operation(s) on the first number. The same operation(s) are followed in all the number pairs, EXCEPT one. Find that odd number pair.

The correct answer is

(10, 100)

Finding the Odd Number Pair Based on Mathematical Operations

The question asks us to identify the number pair that does not follow the same mathematical rule as the other pairs. In each pair $(a, b)$, the second number ($b$) is derived from the first number ($a$) using a specific operation or set of operations. We need to find the common operation among most pairs and then spot the one that deviates.

Analyzing the Given Number Pairs

Let's examine each pair and try to find a relationship between the first number and the second number.

  1. (8, 62): Let the first number be $n=8$. We need to see how 62 can be obtained from 8. Trying simple operations:
    • Addition/Subtraction: $8 + 54 = 62$ (Unlikely to be a general rule)
    • Multiplication: $8 \times ? = 62$ (Not a whole number)
    • Squaring: $8^2 = 64$. How is 62 related to 64? $64 - 2 = 62$. This suggests a potential rule: $n^2 - 2$.
    Let's test this potential rule $n^2 - 2$ on the other pairs.
  2. (10, 100): Let the first number be $n=10$. Applying the potential rule $n^2 - 2$: $10^2 - 2 = 100 - 2 = 98$. The second number in the pair is 100, not 98. Let's see the direct relationship for this pair: $10^2 = 100$. This pair follows the rule $n^2$.
  3. (14, 194): Let the first number be $n=14$. Applying the potential rule $n^2 - 2$: $14^2 - 2 = 196 - 2 = 194$. The second number in the pair is 194. This pair follows the rule $n^2 - 2$.
  4. (12, 142): Let the first number be $n=12$. Applying the potential rule $n^2 - 2$: $12^2 - 2 = 144 - 2 = 142$. The second number in the pair is 142. This pair follows the rule $n^2 - 2$.

Identifying the Rule and the Odd Pair

From the analysis above, we can see the following relationships for each pair $(n, \text{second number})$:

Number Pair First Number ($n$) Second Number Operation Found
(8, 62) 8 62 $8^2 - 2 = 64 - 2 = 62$ (Rule: $n^2 - 2$)
(10, 100) 10 100 $10^2 = 100$ (Rule: $n^2$)
(14, 194) 14 194 $14^2 - 2 = 196 - 2 = 194$ (Rule: $n^2 - 2$)
(12, 142) 12 142 $12^2 - 2 = 144 - 2 = 142$ (Rule: $n^2 - 2$)

It is clear that pairs (8, 62), (14, 194), and (12, 142) all follow the rule where the second number is obtained by squaring the first number and subtracting 2 ($n^2 - 2$).

The pair (10, 100) follows a different rule, where the second number is simply the square of the first number ($n^2$).

Therefore, the odd number pair that does not follow the same operation as the others is (10, 100).

Conclusion

The common mathematical operation connecting the number pairs is squaring the first number and subtracting 2 ($n^2 - 2$). The pair (10, 100) does not follow this rule, instead following the rule of simple squaring ($n^2$). Thus, (10, 100) is the odd number pair.

Revision Table: Checking Number Pair Operations

Pair First No. ($n$) Calculate $n^2 - 2$ Given Second No. Match?
(8, 62) 8 $8^2 - 2 = 64 - 2 = 62$ 62 Yes
(10, 100) 10 $10^2 - 2 = 100 - 2 = 98$ 100 No
(14, 194) 14 $14^2 - 2 = 196 - 2 = 194$ 194 Yes
(12, 142) 12 $12^2 - 2 = 144 - 2 = 142$ 142 Yes

This table clearly shows that (10, 100) is the outlier.

Additional Information: Number Pattern Reasoning

Questions like this test your ability to find patterns in numbers. Common patterns involve basic arithmetic operations (addition, subtraction, multiplication, division), squares, cubes, square roots, or combinations of these. When solving such problems, it's helpful to:

  • Look for simple relationships first.
  • Test common operations like squaring or cubing the number and adding/subtracting/multiplying by a constant.
  • Compare the difference or ratio between the numbers.
  • Systematically test potential rules across all given pairs to find the consistent one.
  • Identify the pair that does not fit the established consistent rule.

This type of problem is common in logical reasoning and quantitative aptitude tests.

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Important Questions from Number Based

  1. Four number-pairs have been given, out of which three are alike in some manner and one is different. Select the number-pair that is different. (Any operation on digits is not allowed)

  2. Four number-pairs have been given, out of which three are alike in some manner and one is different. Select the number-pair that is different.

  3. Four number-pairs have been given, out of which three are alike in some manner and one is different. Select the number-pair that is different.

  4. Four number-pairs have been given, out of which three are alike in some manner and one is different. Select the number-pair that is different.

  5. Four number-pairs have been given, out of which three are alike in some manner and one is different. Select the number-pair that is different.

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