42 Is 30 Percent of What Number

42 Is 30 Percent of What Number: Unveiling the Mystery


Mathematics is a fascinating subject that constantly challenges our logical thinking and problem-solving skills. One such intriguing problem is determining a number when we know that it is a certain percentage of another number. In this article, we will explore the question, “42 is 30 percent of what number?” and unravel the mystery behind it. We will also address some frequently asked questions to provide a comprehensive understanding of the topic.

Understanding Percentages

Before delving into the problem at hand, let’s briefly recap what percentages are and how they relate to numbers. A percentage represents a portion of a whole, with 100% being equal to the entire amount. It is denoted by the symbol “%.” Percentages are commonly used to describe parts of a whole in various contexts, such as discounts, interest rates, or statistical data.

The Problem: 42 is 30 Percent of What Number?

Now, let’s focus on the problem at hand: 42 is 30 percent of what number? To find the unknown number, we can set up a proportion using the concept of percentages. Let x represent the unknown number. We can then write the proportion as follows:

42 / x = 30 / 100

To solve this proportion, we can cross-multiply and find the value of x:

42 * 100 = 30 * x

4200 = 30x

Dividing both sides of the equation by 30, we get:

x = 140

Therefore, 42 is 30 percent of 140.


1. What is a proportion?

A proportion is an equation that states that two ratios or fractions are equivalent. In our problem, we set up a proportion where the ratio of 42 to x is equal to the ratio of 30 to 100.

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2. Are there alternative methods to solve this problem?

Yes, there are alternative methods to solve this problem. One such method is using cross-multiplication, as demonstrated above. Another approach is to convert the percentage into a decimal and then solve for the unknown number.

3. Can this problem be solved using a calculator?

Yes, a calculator can be used to solve this problem. By inputting the equation 42 / x = 30 / 100, you can solve for x directly on a calculator.

4. Are percentages useful in real-life situations?

Yes, percentages are commonly used in various real-life situations. They are used to calculate discounts during sales, determine interest rates on loans, represent statistical data, and much more. Understanding percentages is essential in making informed decisions and analyzing numerical information.

5. Can percentages be greater than 100%?

Yes, percentages can be greater than 100%. A percentage greater than 100% indicates that the value is more than the whole amount. For example, if you have 120% of something, it means you have the whole amount plus an additional 20%.


In conclusion, determining a number when it is a certain percentage of another number is a common math problem. By setting up a proportion and solving for the unknown, we can find the value we seek. In the case of “42 is 30 percent of what number,” the answer is 140. Percentages play a vital role in various aspects of our lives, and understanding them is crucial for making informed decisions. So, the next time you encounter a similar problem, rest assured that armed with the knowledge of proportions and percentages, you will be able to solve it with ease.

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