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# Maths Help Videos

The Maths help videos are displayed categorized by Primary Grade and then by mathematical Strand. Where videos content exceeds the skills appropriate to a grade, the video will be associated to all relevant grades.

We would like to thank Khan Academy for sharing it's mathematical related videos on 4to12maths.com Note: All Khan Academy content available for free at www.khanacademy.org

### Algebra

 Adding integers with different signs Adding integers with different signs. Find the sum of -15 + (-46) + 29. Shows how to do this using the number line. Adding negative numbers Adding negative numbers e.g. Find the sum of -15 + (-46) + (-29). Shows how to do this using the number line. Adding/Subtracting negative numbers Adding and subtracting negative numbers. Ordering negative numbers. Ordering negative numbers from least to greatest, -25, -30, -7, -10, -40.

### Number

 Adding two decimal numbers Adding two decimal numbers together eg. 0.0085 + 1.799, 5875 + .028, 102.1 + 2.56. This introduces the concept of alignment of the decimal points. Subtracting two decimal numbers Subtracting two decimal numbers from one another. The concept of alignment of the decimal place is covered along with borrowing or renaming. Examples used are the following: 5.73 - 0.0821, 8.25 - 0.0105, 2.64 - 0.00486. Multiplying decimals Multiplying decimals. Explanation of how to deal with the decimal point in these types of questions. e.g. 75.18 x 0.97, 5.10 x 1.09, .0075 x 1.5. Introduction to lattice multiplication Explain lattice multiplication and how it works along with two examples: 27 x 48, 5479 x 787. Please note that lattice multiplication is not a methodology taught in Irish Primary schools but we thought we would include it to show that there are other ways to multiply numbers together Explanation of why lattice multiplication work Explanation of why lattice multiplication works. Two examples: 27 x 48, 5479 x 787. Please note that lattice multiplication is not a methodology taught in Irish Primary schools but we thought we would include it to show that there are other ways to multiply numbers together. Dividing a two digit number into a larger number Long division approach to division with and without remainders. Dividing a 4 digit number by 2 digit number eg. 6250 divided by 25, 2265 divided by 15, 5578 divided by 67. Expressing fractions as decimals. Expressing decimals as fractions. Expressing fractions (proper and improper) as decimals. Expressing decimals as fractions. Expressing percentages as decimals & decimals as percentages. Expressing percentages as decimals. Expressing decimals as percentages. Dividing decimal numbers Dividing decimal numbers using long division method. e.g. 23.828 divided by 0.28, 43.23 divided by 3.3, 0.3350 divided by 2.5 Converting percentages and fractions to decimals to order numbers Converting percentages and fractions to decimals to order numbers. Calculated the Greatest Common Factor / Divisor of numbers Calculated the greatest common factor / divisor of two numbers eg.(12,8), (25,20), (5,12) and (6,12). Calculated the Least Common Multiple of numbers Calculated the Least Common Multiple of numbers eg. (10,8). Expressing mixed numbers as improper fractions & fractions as mixed numbers Expressing mixed numbers as improper fractions. Expressing improper fractions as mixed number. How much time between two times How much time between two times eg. 1.25pm and 3.16pm, 9.16am and 10.17pm. Using the timeline approach and 24hr clock approach. Calculating time differences across different time zones Calculating time differences across different time zones eg. What is the time difference between 1.25pm and 3.25pm. Using the time line approach and the subtraction approach for both 12hr and 24hr clocks. Defining and identifying Prime Numbers Defining and identifying Prime Numbers. Rounding Whole Numbers to the nearest hundred. Round 24,259 to the nearest hundred. Introduces us to the concept of "Rounding Up" and "Rounding Down" of a number. Visualising the problem on the number line. Place Value 3 : Write a number in expanded form. Write 14,897 in expanded form. Rounding Whole Numbers to the nearest thousand. Round 423,275 to the nearest thousand. Introduces us to the concept of "Rounding Up" and "Rounding Down" of a number. Visualising the problem on the number line. Rounding Whole Numbers to the nearest ten Round 1,585 to the nearest ten. Introduces us to the concept of "Rounding Up" and "Rounding Down" of a number. Partial quotient division: An alternate to traditional long division. This video shows the long division method for division as well as an alternative method for dividing called Partial quotient method. The example shown for both is: 1,388 divided by 16. Partial quotient division 2: An alternate to traditional long division. This video shows the long division method for division as well as an alternative method for dividing called Partial quotient method. The example shown for both is: 9,873,952 divided by 291.

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