Hello, I'm Kiley, and welcome to Problem Solving Strategy 7: Use a Number Line.
I bet you didn't know how powerful number lines can be when solving math problems.
Let me show you how this tool can help you.
A number line is simply a visual with numbers in order on a line.
It can help you find an answer to a problem by moving left or right on the number line.
Let's look at some examples to understand what I mean.
A number line can help us add.
"Megan had 4 books.
She picked up 5 more books at the library.
How many books does she have in all?"
In this problem, we know we need to add since we want to know how many books in all that Megan had.
On a number line, adding would look like this.
Megan has 4 books, so we'll start at the number 4.
She then adds 5 more books, so we'll jump 1, 2, 3, 4, 5 spots,
and land here, at number 9.
And that's how many books Megan has in all.
4 + 5 = 9
We're right.
You'll notice that when we added, we move toward the right
from our beginning number,
and moved forward 5 spaces to get our final answer.
A number line can also help us to subtract.
Can you guess what direction we'll move
when we're subtracting using a number line?
Yes. You got it.
Since we moved right when we added, we will move left to subtract.
Here's a word problem to prove it.
"The following week, Megan returned 7 books to the library.
She did not finish reading all of them.
How many books did she keep?"
Hmm...
Well, we know from the other problem that Megan borrowed a total of 9 books,
so we'll start at 9 on the number line.
She returned 7 books.
So that means Megan has less books after her visit to the library.
We will subtract by moving left
1, 2, 3, 4, 5, 6, 7 times.
That leaves Megan with 2 books.
That makes since, since 9 - 7 is 2.
Just like adding, when we use a number line to subtract,
we start at the number we were originally given,
and then we move left on the number line however much we are subtracting by.
After that is finished, we are at the answer.
Number lines can also be used to solve problems where you'll need to multiply or divide,
skip count, find fractions, compare measurements, and even to calculate differences in time.
Solve the math word problems in our fun online games and quizzes.
Keep practicing problem solving, and remember to always be clever.