How many ways do you think there are to subtract? Are they the same as for addition? Think about it.
Would a number line work for subtracting like it did for addition?
Today you will try some different ways to take away. More practice will make it easier to solve subtraction problems.
After you finish today's lessons, you will know the answers to these questions.
1. How many can you do in two minutes? Watch the signs!
a. 18 - 9 = ________ f. 9 + 5 = ________ k. 8 + 6 = ________ p. 14 - 7 = ________ b. 9 + 6 = ________ g. 10 - 2 = ________ l. 9 + 9 = ________ q. 10 + 10 = ________ c. 8 + 6 = ________ h. 9 - 4 = ________ m. 12 - 6 = ________ r. 8 + 8 = ________ d. 9 - 2 = ________ i. 9 + 7 = ________ n. 7 - 6 = ________ s. 5 + 4 = ________ e. 9 - 7 = ________ j. 20 - 10 = ________ o. 7 + 7 = ________ t. 6 + 6 = ________
How many did you do?
2. Solve these problems. For each problem, write the number sentence, including the addition or subtraction sign. Then answer the problem in a complete sentence.
a. Su Ling climbed nine steps. She then climbed six more steps. How many did she climb in all?
_____ _____ _____ = _____
b. Marnie has 14 dollars. Marnie's brother has 6 dollars. How many more dollars does Marnie have than her brother?
_____ _____ _____ = _____
c. Mabel found seven pencils in her desk. She already has nine pencils in her pencil case. How many pencils does Mabel have now?
_____ _____ _____ = _____
Elena showed Jasper some ways to help make subtraction easy. She showed him the number line from Day 10. Elena told Jasper he could use the number line for adding and subtracting.
1. Solve these problems with the number line.
a. Matthew had 13 balloons. Then 4 balloons burst. How many does he have now?
Write the number sentence. _____ - _____ = _____
b. There are 19 pages in your science booklet. You have read 12 pages. How many pages do you have left to read?
Write the number sentence. _____ - _____ = _____
2. Try these on your ruler.
a. 14 - 5 = ________ d. 18 - 5 = ________ b. 11 - 3 = ________ e. 15 - 4 = ________ c. 19 - 2 = ________ f. 12 - 9 = ________
3. Try these on the number line.
a. 16 - 10 = ________ d. 17 - 14 = ________ b. 20 - 13 = ________ e. 13 - 6 = ________ c. 19 - 17 = ________ f. 15 - 4 = ________
Counting back is another way of subtracting.
Write the numbers in order counting backward.
| 20 | 19 |
1. Count back from 15.
15 - 3 = ________ 15, ________, ________, ________
2. Count back from 8.
8 - 2 = ________ 8, ________, ________
3. Count back from 17.
17 - 1 = ________ 17, ________
4. Count back from 12.
12 - 3 = ________ 12, ________, ________, ________
Counting on is another way of subtracting. To subtract this way, count on from the lower number.
It may help the student initially to use fingers to add on.
For example, 9 - 7 = ________.
Count 7, . . . 8, 9.
You counted 2 on, so 9 - 7 = 2.
14 - 11 = ________
Begin with 11 and count on until you reach 14. How many is that?
11, . . . 12, 13, 14.
So, 14 - 11 = 3.
8 - 5 = ________
Begin with 5. Count on until you reach 8. How many is that?
Count 5, . . . 6, 7, 8.
So, 8 - 5 = 3.
Subtract these by counting on. Remember to count on from the smaller number.
| 1. 19 - 18 = ________ | 4. 20 - 17 = ________ | |
| 2. 13 - 11 = ________ | 5. 16 - 15 = ________ | |
| 3. 17 - 14 = ________ | ||
Go to the assignment for Day 11.
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