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Question

(x % of y) + (y % of x) is equivalent to.

The correct answer is

2 % of xy

To find what the expression \( (x \% \text{ of } y) + (y \% \text{ of } x) \) is equivalent to, we need to understand how to convert percentages into mathematical expressions.

Percentage Conversion Basics

The term 'percent' literally means 'per one hundred'. So, \( P \% \) can be written as \( \frac{P}{100} \). When we say 'P % of Q', it means \( \frac{P}{100} \times Q \).

  • Understanding 'x % of y':

    This expression can be written mathematically as:

    \( x \% \text{ of } y = \frac{x}{100} \times y = \frac{xy}{100} \)

  • Understanding 'y % of x':

    Similarly, this expression can be written as:

    \( y \% \text{ of } x = \frac{y}{100} \times x = \frac{yx}{100} \)

Combining the Expressions

Now, let's add the two expressions together as given in the problem:

\( (x \% \text{ of } y) + (y \% \text{ of } x) = \frac{xy}{100} + \frac{yx}{100} \)

Since \( xy \) is the same as \( yx \) (due to the commutative property of multiplication), we can write:

\( \frac{xy}{100} + \frac{xy}{100} \)

When adding fractions with the same denominator, we add their numerators:

\( = \frac{xy + xy}{100} = \frac{2xy}{100} \)

Comparing with Options

We need to find an option that is equivalent to \( \frac{2xy}{100} \).

Option Mathematical Expression Result Comparison
1. 2 % of xy \( \frac{2}{100} \times xy \) \( \frac{2xy}{100} \) Matches our result
2. 2 % of (xy/100) \( \frac{2}{100} \times \left(\frac{xy}{100}\right) \) \( \frac{2xy}{10000} \) Does not match
3. xy % of 100 \( \frac{xy}{100} \times 100 \) \( xy \) Does not match
4. 100 % of xy \( \frac{100}{100} \times xy \) \( xy \) Does not match

From the comparison, Option 1, which is \( 2 \% \text{ of } xy \), exactly matches our derived result of \( \frac{2xy}{100} \).

Final Conclusion

The expression \( (x \% \text{ of } y) + (y \% \text{ of } x) \) simplifies to \( \frac{2xy}{100} \), which is equivalent to \( 2 \% \text{ of } xy \). This demonstrates the fundamental rules of percentage calculation and algebraic manipulation.

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Important Questions from Numerical Estimation

  1. The number of digits you have to type to write all the page numbers of a book starting from I (first page) is 2019. What is the number of pages in that book?

  2. 1200 men and 500 women can build a bridge in 2 weeks. 900 men and 250 women will take 3 weeks to build the same bridge. How many men will be needed to build the bridge in one week?

  3. The number of 3-digit numbers such that the digit 1 is never to the immediate right of 2 is

  4. Given \({\left( {9{\rm{\;inches}}} \right)^{\frac{1}{2}}} = {\left( {0.25{\rm{\;yards}}} \right)^{\frac{1}{2}}}\). Which one of the following statements is TRUE?

  5. Two and a quarter hours back, when seen in a mirror, the reflection of a wall clock without number markings seemed to show 1:30. What is the actual current time shown by the clock?

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