SUBTRACTION

Subtraction is the same as TAKE-AWAY. When the number you are subtracting is small, you can just count backwards:

10-2: Think 10, 9, 8

7-3: Think 7, 6, 5, 4

12 - 1: Think 12, 11

When the number being subtracted is big, you want to count the other way.

10-8: Think how many MORE do I need to get from 8 to 10: 2 more

9-6: Think how many MORE do I need to get from 6 to 9: 3 more

When the top number is bigger than 10, we will use the BUILD TO 10 strategy.

14

-7

For each number, we need to figure out how far each number is away from 10.

For our 14, the answer is EASY - as we did in the previous section we know that 10 + 4 = 14, in fact it will just be the second digit of the number: 4.

For our 7, we will use a quick and easy number chart to find out:

 1 2 3 4 5 9 8 7 6 5

To make this table, write the numbers 1 through 5. Below the 5, write another 5 and then writing to the LEFT, continue to 9. Each pair should add to 10 if you did it right. So, if we want to find out how far 7 is from 10, we look on the chart for it's partner: 3.

Once we find the distance from 10 for both numbers, we add those two numbers together: 4 + 3 = 7 and that is our answers.

Sometimes it is easy to remember: Copy (the ones digit), Partner (use the table), and Add.

Examples: Note that the first number is just copied from the ones place, the second number is the partner from the table, then I add.

 13 -7 3 +3 6 15 -8 5 +2 7 14 -6 4 +4 8 14 -5 4 +5 9

Let's do it one step at a time together:

First how far from 10 are these numbers:

13 Answer 16 Answer 17 Answer 12 Answer 19 Answer 18 Answer 11 Answer 14 Answer 15 Answer Use the chart to figure out how far these numbers are from 10?

2 Answer 6 Answer 5 Answer 9 Answer 7 Answer 8 Answer 1 Answer 3 Answer 4 Answer Now to convert from a subtraction problem to an addition problem - build each to 10 and add the two numbers:

1. 14 - 7 Answer 2. 15- 9 Answer 3. 16 - 8 Answer 4. 12 - 5 Answer 5. 15- 7 Answer 6. 13 - 6 Answer 7. 17 - 9 Answer 8. 16 - 7 Answer 9. 14 - 6 Answer 10. 13 - 8 Answer 