## Solving Simple Subtraction Problems Using a Number Line.

I am learning to solve simple subtraction problems by counting back on a number line.

I know I can do it when I can using the counting back strategy on a number line to solve subtraction problems.

Yesterday we used the counting back strategy to solve subtraction problems. You can also use the counting back strategy with the help of a number line to solve subtraction problems.

Watch the video below if you’re unsure how to use a number line to solve a subtraction problem.

### Challenge

Can you solve the cards in your head without using a number line or counting on your fingers?

If you can, share the strategy that you are using with a family member.

Print and cut the cards up or write them on paper and cut them up. Place the cards face down and flip to reveal the sum. See how quickly you can solve each problem.

You could even add to the cards by using these sums-

27-10 =

26-5 =

28-15 =

22-16 =

21- 9 =

## Subtraction Using the Counting Back Strategy

I am learning to use the counting back strategy to solve subtraction problems.

I know I can do it when I am counting back from the biggest number in a subtraction problem.

This week we are looking at solving subtraction problems, focusing on counting back from the largest number. Learning to do this allows us to subtract from a collection of objects much quicker.

To complete today’s task, you will need some playing cards or two dice. If you don’t have any, follow this link for some online dice.

Using cards:

• Remove all of the picture cards and the 10s from your deck so that you only have Aces through to 9s.
• Choose two cards from your deck (eg. 3, 4).
• starting from the biggest number, use the counting back strategy to work out what you would have left if you subtracted the smallest number from the largest number (4-3=1).
• On a piece of paper, write down the subtraction problem that you have solved.

Using dice:

• Roll two dice (10 sided if you have them)
• starting from the biggest number, use the counting back strategy to work out what you would have left if you subtracted the smaller number on the dice from the largest number on the dice (4-3=1).
• On a piece of paper, write down the subtraction problem that you have solved.

Repeat this process at least 5 times.