If you look in the newspapers and listen on the television you will notice that people normally use rounded numbers in discussion.
When is the last time you read a newspaper article that said that the population of Moscow was 12,480,481 or that last year’s profit of Dodo Pizza was $314,291,836?
Why do people round numbers?
When we round numbers we must give the number as close to the actual number as possible, but without the same number of non-zero digits.
So if we round to the nearest 10, where should we round 813 too? How about 819? How about 815?
How about 874?
Here we are going to round to the nearest hundred. What do you think 623 will round to? What about 673? What about 649? What about 650?
Let’s try these practice questions in our notebook (from exercise 5A on pages 71 and 72 of your notebook):
Here are the answers to the above exercise:
We also need to thing about numbers that are not whole numbers (that people often call decimal numbers), e.g. 234.925
We could be asked to round these to the nearest tenth or to the nearest hundredth.
We may also be asked to round them to one decimal place or to two decimal places. What does this mean? How would we do it with the above number.
What is 2.763 to 1 decimal place? What is it to 2 decimal places?
Let’s try the questions below (from exercise 5B on page 72 of the textbook):
Below are the answers to the above questions: