Addition and Subtraction Chapter Notes | Mathematics for Primary 6 PDF Download

Introduction

Mathematics is like a fun adventure, and addition and subtraction are the trusty tools that help us solve everyday puzzles! Whether it's counting the total number of books in a library or finding out how much money is left after a big purchase, these operations make life easier. In this chapter, we'll dive into the exciting world of adding and subtracting large numbers, discovering how to handle missing digits, estimate results, and create real-life word problems. Get ready to explore these skills step-by-step and become a math wizard!

Addition

Addition means combining two or more numbers, called addends, to find their total, known as the sum.
Steps to add numbers:

• Arrange the numbers in columns based on their place values (ones, tens, hundreds, etc.).
• Start adding from the rightmost column (ones place) and move left to larger place values.
• Write the sum below each column.

Addition of Large Numbers (without carry over)

Add large numbers by aligning them in columns according to place values. Start from the ones place and add each column moving left to tens, hundreds, thousands, etc. No carry over occurs when the sum of digits in a column is less than 10.

Addition of Large Numbers (with carry over)

• When the sum of digits in a column is 10 or more, write the ones digit and carry over the tens digit to the next column. Add the carried-over digit with the digits in the next column. Continue this process for each column moving left.

Finding the Missing Digits

Use place values to find missing digits in addition problems.
Steps to find missing digits:

• Start with the ones column and check the sum.
• If the sum has a specific ones digit, find the number that, when added to the known digit, gives the sum (considering carry overs).
• Move to the next columns (tens, hundreds, etc.), accounting for any carry overs from previous columns.
• Continue until all missing digits are found.

Estimating the Sum

Estimation gives an approximate sum close to the actual sum.
Steps to estimate:

• Round each addend to the nearest 10, 100, 1,000, etc., based on required accuracy.
• Add the rounded numbers to get the estimated sum.
• Compare with the actual sum to check closeness.

Word Problems on Addition

Word problems involve adding numbers to solve real-life situations.
Steps to solve:

• Identify the numbers to be added from the problem.
• Add the numbers using column addition, handling carry overs if needed.
• Write the final answer with appropriate units (e.g., books, people).

Framing Word Problems on Addition

Create word problems by using given numbers to describe real-life scenarios.
Steps to frame:

• Choose a context (e.g., money, population, items).
• Use the given numbers as quantities in the scenario.
• Form a question asking for the total sum.

Subtraction

Subtraction means taking away one number (subtrahend) from another (minuend) to find the difference. It is the opposite of addition.
Steps to subtract:

• Arrange numbers in columns by place values.
• Subtract from the ones place, moving left to larger place values.
• Write the difference below each column.

Subtraction of Large Numbers (without borrowing)

Subtract large numbers by aligning them in columns by place values. Start from the ones place and subtract each column moving left. No borrowing is needed when the minuend’s digit is larger than or equal to the subtrahend’s digit in each column.

Subtraction of Large Numbers (with borrowing)

When the minuend’s digit is smaller than the subtrahend’s digit, borrow 1 from the next higher place value. Reduce the higher place value by 1 and add 10 to the current place value. Subtract the digits and continue to the next columns.

Subtraction with Zeros

When subtracting from a number with zeros, borrowing can involve multiple columns.
Steps:

• If the minuend’s digit is 0 or smaller than the subtrahend’s digit, borrow from the next non-zero place value.
• Adjust the place values accordingly (e.g., borrow 1 from thousands, give 10 to hundreds, then to tens, then to ones).
• Subtract column by column.

Checking Subtraction through Addition

To check if subtraction is correct, add the difference and the subtrahend. If the sum equals the minuend, the subtraction is correct; if not, it’s incorrect.
Steps to check:

• After subtracting, take the difference and add it to the subtrahend.
• Compare the result with the minuend.
• If they match, the subtraction is correct.

Finding the Missing Digits

Use place values and subtraction formulas: Difference = Minuend - Subtrahend, or Minuend = Difference + Subtrahend, or Subtrahend = Minuend - Difference.
Steps:

• Start with the ones column and use the appropriate formula to find the missing digit.
• Account for borrowing in previous columns if needed.
• Move to the next columns, repeating the process.

Estimating the Difference

Estimation gives an approximate difference close to the actual difference.
Steps:

• Round the minuend and subtrahend to the nearest 10, 100, 1,000, etc.
• Subtract the rounded numbers to get the estimated difference.
• Compare with the actual difference to check accuracy.

Word Problems on Subtraction

Word problems involve subtracting numbers to solve real-life situations.
Steps to solve:

• Identify the minuend and subtrahend from the problem.
• Subtract using column subtraction, handling borrowing if needed.
• Write the final answer with appropriate units.

Framing Word Problems on Subtraction

Create word problems by using given numbers in real-life scenarios.
Steps to frame:

• Choose a context (e.g., money, population, items).
• Use the given numbers as the minuend and subtrahend.
• Form a question asking for the difference.