Rounding and estimations.

Rounding and Estimations

Lesson One

​Benjamin Franklin said. " A place for everything, everythings in it place." In math numbers have a place too. In fact the placement of a digit, ( a number 1-9) in a number is very important. It tells us the value of that digit.

In this lesson we will learn place value and use it to round numbers and estimate numbers.

​Objectives

• Identifiy the place value of a digit in a whole number.

• Round and estimate with whole numbers.

​Vocabulary Words

Digit- one of the numerals 0 - 9

Estimate- an apporximate value close to the actual value.

Place value- the position of a digit in a whole numbrer, which determines the value.

​Place Value

​For example

The numbers 420 and 204 have the same digits and same number of digits. However, the digits are in a different order, so the numbers have different values.

​Place number of a digit in a number is its value. It determines the value, or worth, of the digit For example. The number 8,739,205 can be read eight million sever hundred thrity-nine thousand two hundred five. Each digit represents a differnt value in the number.

​Take a Look

​8,739,205

​milllons

​hundred thousands

ten thousands

thousands

hundreds

tens

ones

​For example

​In the following number which digit is in the thousands?

35,768

Beginning from the number 8, which is in the ones place, the 6 in the tens place, the 7 in the hundreds place, and the 5 in the thousands place.

​Example

​How do you read the following number?

480, 232

​Solution

​Using the place value, it reads " Four hundred eighty thousand two hundred thirty-two."

Multiple Choice

In the following number which digit is in the hundred thousands place?

6,741,623

• 5

• 7

• 6

• 3

Multiple Choice

In the following number which place value is held by the 7?

943,712

• ten thousands

• thousands

• hundred thousands

• ones

Multiple Choice

Which of the following number is read, "six thousand, three hundred fifty."

• 3,530

• 6,350

• 5,306

• 6,050,450

Multiple Choice

Which of the following numbers has a 7 in the hundreds place, a 2 in the ones place, and a 4 in the thousands plac?

• 344,732

• 40,752

• 14,728

• 204,732

​Sometimes when we're working with numbers, we dont have to use exact values. For example, a candy bar at the store costs 48 cents. If you plan to buy four candy bars, it's easier to figure out your total cost by first rounding the cost of each candy bar to 50 cents. Then, you can say that the cost of four candy bars is about $2.00. This total is called an estimate because it is close to the actual amount.

There are some rules for rounding numbers and making estimates. To round numbers to a certain place values, we actually look at the place directly to the right of it. If the value to the right is 5 or larger, we round the digit up. If the value to the right is less than 5 we keep the digit the same. Then, the rest of the digit become zeros. Lets look at an example.

Round 3,751 to the nearest hundred.

Notice that the 7 is in the hundreds place. The number to the right of it is a 5. Since this value is 5 or larger, we're gong to round the digit in the hundreds place up. So, the 7 than becomes 8. Then, all the digits to the right of the hundreds place becomes zeros. The number 3,751 rounded to the nearest is 3,800.