Counting backwards

Counting backwards

Lessons

In this lesson, we will learn:

  • How do we count backwards using: the numbers 9 to 0, number lines (and negative numbers), and big numbers (up to millions)?
  • Counting Backwards can help us write subtraction statements.

Notes:

  • We use numbers to represent how many things there are.
    • You can do the exact opposite of normal counting by counting BACKWARDS:
    • 10, 9, 8, 7, 6, 5, 4, 3, 2, 1…

  • Counting backwards means the counting numbers are getting SMALLER
    • If you look at a number line, counting forwards means going from right to left

Counting: Counting Backwards

  • Negative numbers also count backward by going from right to left on a number line
    • Don’t get confused! The negative numbers (digits) are going forwards, but they have a negative sign!
    • The bigger your negative, the smaller your value (more negative = smaller)
    • Ex. counting backwards in negatives: -1, -2, -3, -4, -5, …

  • Recall: number PLACE VALUES!

Counting: Counting Backwards

    • The smaller place values are on the right, the bigger place values are on the left
    • When the digit decreases (from 9 to 0): after you hit 0, next you will decrease 1 FROM the place value on the left. Your digit will then start again from 9 (and count down to 0, repeating the process)

  • You can also use your fingers to count backward and find out how many numbers you have decreased (counted down) by.
    • Put down all your fingers (zero fingers up) when you start on your first number.
    • Each number you count down, raise one more finger.
    • When you reach your last number, you can count your raised fingers
    • Ex. counting from 32 down to 27: you count down by five

Counting: Counting Backwards

  • This can allow you to make subtraction statements!
    • [starting #] – [how much you counted down] = [last #]
    • Ex. counting from 32 down to 27, the subtraction statement is: 32 – 5 = 27
  • Introduction
    Introduction to Counting Backwards:
    a)
    How do we count backwards?

    b)
    How do we count backwards with negative numbers?

    c)
    How do we count backwards with big place values?

    d)
    How can we use counting backwards to understand subtraction?


  • 1.
    Counting backwards to find the next numbers
    Fill in the next four blanks after each number by counting backwards.
    a)
    52, ___, ___, ___, ___

    b)
    376, ___, ___, ___, ___

    c)
    4801, ___, ___, ___, ___

    d)
    90 002, ___, ___, ___, ___

    e)
    1 354 678, ___, ___, ___, ___

    f)
    -5, ___, ___, ___, ___

    g)
    -998, ___, ___, ___, ___


  • 2.
    Counting backwards to find numbers between
    List the numbers in between the given numbers by counting backs.
    a)
    65 and 58

    b)
    2304 and 2295

    c)
    41 003 and 40 997

    d)
    -894 and -902


  • 3.
    Counting backwards and subtraction statements
    Count backwards to find the difference between two numbers. Then, rewrite as a subtraction statement.
    a)
    571 and 566

    b)
    280 643 and 280 632

    c)
    4 000 002 and 3 999 995

    d)
    -94 and -104


  • 4.
    Counting backwards word problem
    Joe entered a contest to guess how many jelly beans there were in a jar! He guessed that there were 1005 jellybeans. He won the contest because he was the closest, but they hold him his guess was too high by 9. How many jelly beans were there exactly?