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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. Two fair dice are thrown. The number of cases where the number appearing on the upper face of the first die is not less than that on the lower face of the second die is

  3. The number of Hens, Ducks, and Goats in farm P are 65, 91 and 169, respectively. The total number of Hens, Ducks and Goats in a nearby farm Q is 416. The ratio of hens : ducks : goats in farm Q is 5 : 14 : 13. All the hens, ducks and goats are sent from farm Q to farm P.

    The new ratio of hens : ducks : goats in farm P is ____________.

  4. A person divided an amount of Rs. 100,000 into two parts and invested in two different schemes. In one he got 10% profit and in the other he got 12%. If the profit percentages are interchanged with these investments he would have got Rs.120 less. Find the ratio between his investments in the two schemes.

  5. S, M, E and F are working in shifts in a team to finish a project. M works with twice the efficiency of others but for half as many days as E worked. S and M have 6 hour shifts in a day, whereas E and F have 12 hours shifts. What is the ratio of contribution of M to contribution of E in the project?

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