Addition & Subtraction

Addition & Subtraction

Addition & subtraction

How do I add large numbers without a calculator?

• There are a variety of written methods that can be used to add large numbers

  • The order in which numbers are added is not important

• The column method is the most commonly used hand written method

  • The numbers are written one number above the other,

    • Line up the digits using place value columns

  • Add each pair of corresponding digits from the top and bottom rows (work right to left)

  • If the result is a single digit

    • write the result in the relevant place value column below the line

  • If the result is a 2 digit number

    • the ones are written in the relevant place value column below the line

    • the tens are carried to the top of the next column

  • If the addition of the final pair of digits results in a 2 digit number 

    • write both digits below the line

• For example, the addition 9789 + 563 = 10 352
  

How do I subtract large numbers?

• A variety of written methods exist, but you only need to know one

  • The order in which two numbers are subtracted is important so ensure the calculation is the right way round

• The column method is the most commonly used hand written method

  • The numbers are written one number above the other

    • Line up the digits using place value columns

    • The number being subtracted should be below the original amount

  • Subtract each digit in the bottom value from the corresponding digit in the top value (work right to left)

  • If the digit being subtracted is bigger than the one it is subtracted from

    •  "borrow ten" from the next column to the left

• For example, 392 - 28 = 364
  

• Another method is counting up

  • E.g. to find 673 - 289 start at 289 and count up

    • Add 1 to get 290

    • Add 10 to get 300

    • Add 300 to get 600

    • Add 73 to get to 673

  • then add the steps together

    • 1+10+300+73=384

    • 673-289=384

What words are used for addition and subtraction?

• Addition may be phrased using the words: plus, total or sum

• Subtraction may be phrased using the words: difference or take away