Grade 3

Grade 3


Fractions and Decimals


In grade 3 math, students learn about fractions and decimals. These are fundamental concepts in math that help us understand parts of a whole and represent numbers that are not whole.

Introduction to fractions

A fraction is a way of representing a part of a whole. Fractions are written with two numbers separated by a line called the fraction bar. The number above the line is the numerator, and the number below the line is the denominator. For example:

1/2

In this fraction, 1 is the numerator and 2 is the denominator.

1/2

The fraction 1/2 means that we have one part of two equal parts of a whole.

Understanding the numerator and denominator

The numerator tells us how many parts we have. The denominator tells us how many equal parts the whole is divided into. In our example:

  • Fraction: 1 (we have one part)
  • Denominator: 2 (the whole is divided into two equal parts)

Types of fractions

Proper fractions

A proper fraction is when the numerator is smaller than the denominator. For example, 3/4 is a proper fraction because 3 is smaller than 4.

3/4

Improper fractions

An improper fraction is when the numerator is greater than or equal to the denominator. For example, 5/4 is an improper fraction because 5 is greater than 4.

Mixed number

Mixed numbers include a whole number and a fraction, such as 1 1/4 which means one whole and one-fourth of the other.

Introduction to decimals

Decimals are another way of representing parts of a whole. Decimal numbers are based on 10.

In decimals a decimal point is used to separate the whole number part from the fractional part. For example:

0.5

The number 0.5 means five-tenths or half.

Understanding place value in decimals

Tenth place

When a number has one digit after the decimal point, that number is in the tenths place. For example:

0.7

Here 7 is in the tenth place, that is, seven-tenth part.

Hundredths place

When a number has two digits after the decimal point, the second digit is in the hundredths place. For example:

0.25

In this number, 2 is in the tenth place, and 5 is in the hundredth place.

Adding fractions to decimals

Both fractions and decimals represent parts of a whole. Let's see how they are related:

  • 1/2 = 0.5
  • 1/4 = 0.25
  • 3/4 = 0.75

Practice exercises

Converting fractions to decimals

  1. Convert 1/5 to decimal:
    1/5 = 0.2
  2. Convert 3/5 to decimal:
    3/5 = 0.6

Converting decimals to fractions

  1. Convert 0.4 to a fraction:
    0.4 = 4/10 = 2/5
  2. Convert 0.8 to a fraction:
    0.8 = 8/10 = 4/5

Adding and subtracting fractions

Same denominator

When adding or subtracting fractions with the same denominators, we add or subtract the numerators:

Example: 1/4 + 2/4 = 3/4

Different denominators

To add fractions with different denominators, first convert them to fractions with the same denominator:

Example: 1/3 + 1/6 = 2/6 + 1/6 = 3/6 = 1/2

Adding and subtracting decimals

Adding and subtracting decimals is just like working with whole numbers, but we need to line up the decimal points:

1.2 + 0.8 ----- 2.0
1.2 + 0.8 ----- 2.0

Subtracting decimals works the same way:

2.5 - 1.3 ----- 1.2
2.5 - 1.3 ----- 1.2

Visual example of fractions and decimals

1/4 and 0.25 visualizations:

Part

1/4

Decimal

The decimal 0.25 is equal to the fraction 1/4. If we look at this on the number line, 0.25 represents one-quarter of the way from 0 to 1.

00.250.50.751

Comparing fractions and decimals

Comparing fractions

To compare fractions with the same denominators, compare numerators:

2/5 is less than 3/5 because 2 is less than 3.

Comparing decimals

To compare decimals, line up their decimal points. The larger decimal is the one with the higher value first, where they differ:

0.4 is less than 0.5.

Conclusion

Understanding fractions and decimals helps us understand numbers that aren't whole. With practice, you'll be able to use these concepts in everyday life, for things like cooking, shopping, and measuring. Keep practicing, and these will become second nature!


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