# Rounding numbers calculator

We use rounding numbers all the time: calculating the household budget, planning trips, analyzing information. It is much easier to remember that there are about a million people in a city than to keep accurate statistics in mind, and when going to the store, it is better to take a round sum with a margin than to try to calculate the spending limit in advance, especially with constantly changing prices.

## History of Rounding Numbers

It's safe to say that rounding numbers to even values began as early as the 7th-6th centuries BC - with the advent of such a universal equivalent as money. But clear mathematical rules about rounding were formulated only in the 19th century - thanks to the outstanding German scientist Carl Friedrich Gauss. It was he who developed and published the rules by which numbers are still rounded.

One of the famous statements of Karl Gauss, which have survived to this day, is the phrase: "The shortcomings of mathematical education are most clearly manifested in the excessive accuracy of numerical calculations." Thus, the German mathematician pointed out that 100% accuracy of calculations is far from always needed, and in some cases it is easier, faster and more appropriate to round off.

The need for rounding numbers was also explained by the primitiveness of computing devices of that time. So, in order to count numbers with 3-10 digits after the decimal point on the accounts (abacus), it was necessary to spend a lot of time and effort, which was far from always justified. If the accuracy of the calculations allowed, the numbers were rounded up to the number of digits that corresponded to the real/actual accuracy of the calculations.

## When rounding numbers comes in handy

In the 21st century, the need for rounding is easily solved with the help of electronic computing devices. A calculator with 8-10 decimal places is installed by default in every mobile phone, not to mention more powerful devices such as PCs and laptops. But in some cases, it’s easier and faster to round off in your head than to take out a gadget and do calculations. For example, rounding might come in handy when:

**Planning purchases.**Knowing the approximate price of each individual product, you can quickly find out their total, rounded cost.**Summarizing information.**For example, if you are asked how many people live in New York, it would be more appropriate to answer "nine million" than "eight million four hundred sixty-seven thousand five hundred thirteen"**Multiplying/dividing large numbers.**Few people can multiply 738 by 46 without a calculator, but if these numbers are rounded (up to 700 and 50), the problem becomes grade 2 mathematics. We multiply 7 by 5, add the remaining zeros to the resulting value, and we get an approximate value - 35000. The exact product of these two numbers is 33948, that is, the error is approximately 3%.

You can round numbers up or down. For example, the first option is necessary when planning purchases - so that there is a reserve in case of a price increase, and the second - to determine the age. So, if your actual age is 28 years and 11 months, in all questionnaires and official documents, you still indicate 28 years.

## Interesting facts

- The seven is considered the most “significant” and “lucky” number in the world. This is not surprising, because there are seven days in a week, there are seven continents on the planet, there are seven colors in the rainbow, and in the Bible there are 7 virtues and 7 deadly sins.
- The largest number is "google", after which the largest American company Google was named. It is written differently - Googol, and is one with 100 zeros or ten to the hundredth power.
- The number pi (π), equal to the ratio of the circumference of a circle to its diameter, is always the same and is a number with an infinite sequence of digits after the decimal point. To simplify calculations, this constant is rounded up to 3.14, but in fact it has no end, and there are thousands of decimal places after the decimal point.
- Despite the fact that zero is the most important number in mathematics, there is no zero year in the chronology system: only 1 BC and 1 AD.
- The number 13 is considered the most unlucky. In many buildings in the West, thirteenth floors, thirteenth rooms and apartments are missing, as people simply refuse to live there. And the number 7 is considered lucky not in all countries, in the same China, 8 (prosperity) and 9 (fullness of heaven and earth) are much more favorable.

It is possible to carry out approximate rounding of numbers in your mind, and for more accurate calculations, special programs and online calculators are used. Depending on the specified parameters, the numbers are rounded up or down with the required accuracy and gradation. Today, such applications are freely available and provided free of charge.