Hopping Frogs: 10 on the Number Line!

Another way to make 10 is on a number line. Number lines might remind you of our numbered stairs on page 16! Number lines are great, especially when frogs are hopping on them.

 

A number line is a line with numbers placed in their correct position. Notice that on a number line, numbers get bigger as we go to the right, and smaller as we go to the left.

We can use number lines to help us add and subtract! If we want to add numbers, we hop to the right, and if we want to subtract (or take away), we hop to the left!

Let’s make 10 on the number line like this: 3 + 7 = 10. We’ll pretend there’s a frog on the 0 and she hops to the 3, since that’s the number we are starting with. Then, to add 7, she just hops 7 spots to the right! And that lands her on the 10.

For 3 + 7 = 10, we could also have the frog start on the 3, and then hop 7 spots to the right. Either way, we land on the 10!

What if we wanted to do the subtraction problem 10 − 7 = 3? Well, the frog would start on the 10, and then hop to the left 7 spots. That would land her on the 3. Try it yourself!

See how it works? And, of course, we can add and subtract other numbers on the number line, too—it doesn’t always have to just be about 10!

When adding numbers on the number line, some teachers will have you start at the first number, and some will want you to start hopping from zero. Both ways will give us the same answer—in this case, 5! Here are two ways it could look:

See how we can either start from the 2, or we can start back at 0 and hop to the 2? Both ways work, but the first way is definitely best for subtraction.