Using Number Lines to Subtract
Basics on the topic Using Number Lines to Subtract
Subtraction on Closed Number Lines
Closed number lines help us see the numbers as we take things away, or subtract. They already have numbers written out for us to use. We always move to the left, or backward, when we subtract on a number line. We subtract with hops on a line to show our work.
Subtraction on a Number Line – Example
Let's practice with the example eighteen minus two. Find the first number, eighteen, and mark it on the number line.
Then, look at the second number, two, and count two spaces to the left, or backward. After counting, we landed on sixteen.
So sixteen is our answer! We write sixteen next to the equal sign. Eighteen minus two equals sixteen!
Subtraction on a Number Line – Summary of Steps
Follow these steps when you need to subtract numbers using a number line:
| Step # | What to do |
|---|---|
| 1 | Start by finding the first number in the problem and marking it on the closed number line. |
| 2 | Look at the second number in the problem and count this number of spaces to the left, or backward. |
| 3 | The number we land on is our answer! |
| 4 | Finally, write the answer next to the equal sign. |
Subtraction on a Number Line – Further Practice
Have you practiced subtraction with number lines worksheets yet? This text deals with teaching number lines for subtraction strategies. Do you want more math activities? After watching the video, you can also find 1st grade subtraction exercises and worksheets with number lines.
Transcript Using Number Lines to Subtract
Mr. Squeaks built a bowling alley for Imani and himself! Mr. Squeaks is up first. He rolls the ball toward the ten pins. Mr. Squeaks knocked over six pins! He wants to know how many pins are still standing. Let's help Mr. Squeaks by "Using Number Lines to Subtract". Closed number lines help us see the numbers as we take things away, or subtract. They already have numbers written out for us to use. We always move to the left, or backward, when we subtract on a number line. We draw hops, or jumps, on the line to show our work. Let's practice with the example eighteen minus two. Find the first number, eighteen, and mark it on the number line. Then, look at the second number, two, and count two spaces to the left, or backward. Let's count back together one, two! We landed on, sixteen, so sixteen is our answer! Write sixteen here next to the equal sign. Eighteen minus two equals sixteen! Now let's help Mr. Squeaks by solving ten minus six to see how many pins are left! Find the first number, ten, and mark it on the number line. Then, look at the second number, six, and count six spaces to the left. Let's count back together: one, two, three, four, five, six! We landed on, four, so four is our answer! Finally, write four here next to the equal sign. Ten minus six equals four so, Mr. Squeaks has four bowling pins left! Mr. Squeaks has one more turn to knock down the last four pins. He knocks down three of them. What is four minus three? Let's use a number line to help us subtract! What do we do first? First, we find four and mark it on the number line. What is our next step? Next, we count back three spaces since the second number is three. What number did we land on? We landed on one, so we write one next to the equal sign. Four minus three equals one, so Mr. Squeaks has one bowling pin left! Before Imani's turn, let's remember! We can use number lines to help us see the numbers we take away when we subtract. Start by finding the first number in the problem and marking it on the closed number line. Then, look at the second number in the problem and count this number of spaces to the left, or backward. The number we land on is our answer! Finally, write the answer next to the equal sign. Let's see how Imani does. Strike! “Well, I guess we don’t need a number line to know how many pins Imani has left!”
Using Number Lines to Subtract exercise
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How many pins are still standing after Mr. Squeaks' turn?
HintsMr. Squeaks started with 10 pins, so start by finding 10 on the number line.
Mr. Squeaks knocked down 7 pins, so we need to count back 7 jumps.
SolutionMr. Squeaks has 3 pins still standing!
- Mr Squeaks started with 10 bowling pins so we find 10 on the number line.
- We then need to count backwards 7 jumps because Mr. Squeaks knocked over 7 pins.
- We land on 3 so that is our answer.
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Complete the bowling card.
HintsFind the starting number on the number line.
For example, if we were solving 7 - 3 we would start at 7.
For example, if we were solving 7 - 3, we would count 3 jumps backwards like this.
SolutionEach player started with 10 pins.
The first ball Mr. Squeaks bowled hit 3 pins so we are solving 10 - 3.
We find 10 on the number line and then count 3 jumps backwards as we can see on the number line above.
We land on 7 so that is the answer.
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Mr. Squeaks' other scores
7 - 6
- Start on 7 and count 6 jumps backwards
- We land on 1
- Start on 10 and count 5 jumps backwards
- We land on 5
- Start on 5 and count 1 jump backwards
- We land on 4
Imani's scores
10 - 9
- Start on 10 and count 9 jumps backwards
- We land on 1
- This time we are not subtracting anything so there are no jumps to make.
- The answer is 1
- Start on 10 and count 4 jumps backwards
- We land on 6
- Start on 6 and count 6 jumps backwards
- We land on 0
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Solve the subtraction problems.
HintsHow many pins did the player start with? Find this number on the number line first.
The number they started with is represented by the pin that is standing up.
How many pins were knocked over? Count backwards this number of jumps to find the answer.
The number of pins knocked over is represented by the pin that has fallen down.
For example, this player started with 10 pins and knocked 5 pins down so we solve 10 - 5 which equals 5.
SolutionThe number line above shows us how to solve the first problem.
We started with 10 pins so we found 10 on the number line.
4 pins were knocked over so we count 4 jumps backwards.
We land on 6 so that is our answer.
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Following the same steps:
- 6 - 5 = 1
- 10 - 1 = 9
- 9 - 7 = 2
- 10 - 3 = 7
- 7 - 4 = 3
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Which are the correct values?
HintsRemember, each player starts with 10 pins so you are subtracting their first throw from 10.
If a player knocked 2 pins down on their first turn we would solve it like this.
10 - 2 = 8
If the player knocked down 3 more pins on their second turn we would solve it like this. Remember, we're now subtracting from 8 because that is how many were left after their first go.
8 - 3 = 5
SolutionMr. Squeaks had 1 pin left standing.
You can see on the number line how this was solved.
Imani had 0 pins left standing.
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- Mr. Squeaks started with 10 pins.
- He knocked down 6 pins on his first throw so we subtract 6 from 10 as shown by the red jumps on the number line.
- This gives us the answer of 4.
- On his second turn he knocked down 3 pins so we now subtract 3 from 4 because that is how many pins were left after his first turn.
- 4 - 3 = 1 (as shown by the blue jumps on the number line).
- After his two throws, Mr. Squeaks had 1 pin left.
- Imani started with 10 pins.
- On their first turn they knocked down 8 pins so we subtract 8 from 10 which equals 2.
- They then knocked down 2 pins on their second throw.
- They only had 2 left standing after their first turn so we subtract 2 - 2 which equals 0.
- Imani knocked all of the pins down and was left with 0 still standing.
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How many pins does Mr. Squeaks have left?
HintsMr. Squeaks started with 10 bowling pins and knocked 8 down.
We are trying to solve 10 - 8. We can use the number line like this to help us.
SolutionMr. Squeaks started with 10 bowling pins so we need to find 10 on the number line.
He knocked over 8 so we need to count 8 jumps backwards.
We land on 2 which is our answer. 2 pins are still standing.
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Mr. Squeaks' seed situation.
HintsUse a number line to help with subtracting.
Think about each subtraction problem carefully. Remember, you are starting with a different number each time.
Solution- Mr. Squeaks has been counting his seeds. He has 14 seeds in the jar.
- The next day Mr. Squeaks went to check on his seeds and found that 3 were missing! He figured out that he now has 11 left.
- 14 - 3 = 11
- He checked on them again the next day and 5 more were missing! He now has 6 left!
- 11 - 5 = 6
- Mr. Squeaks checked on them again the next day and found that 6 more were gone! He now has 0 seeds!
- 6 - 6 = 0
- Imani has found a baby hamster! So that's where all the seeds have gone!
