Open Number Lines Explained

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Strategies for teaching addition and subtraction using open number lines, a Common Core 2nd grade math skillIf Not the Algorithm, Then What?

The summer time earlier than my college was implementing Common Core math requirements, all of us attended a Three-day coaching.  In 2nd grade we deal with “regrouping” (or borrowing and carrying) as well as and subtraction.  It’s an enormous deal for us, it’s our factor, and we’re proud to teach this important talent.

I keep in mind the coach saying, “you don’t need to be teaching them the algorithms for addition and subtraction anymore.”  What?!?  I’m undecided what I used to be extra uncomfortable with, the laborious pupil desk I used to be sitting in, or the concept of not educating the algorithm anymore!   Surely this coach didn’t know what she was speaking about.  Someone was courageous sufficient to elevate their hand and ask, “so, if we aren’t teaching the algorithm, how will the kids learn to add and subtract numbers that need regrouping?”

The coach calmly mentioned, “Well here’s one way, it’s called an open number line.”  I’m certain we appeared identical to our amazed 2nd graders as we watched her sketch outlines and jumps and resolve issues on quantity strains that solely contained just a few landmark numbers.

Quick Start Guide

Here are some necessary issues to know concerning the open quantity line technique:

*used to mannequin addition, subtraction, fractions, and time (these are simply the methods I’ve used them)
*college students begin with a clean line and solely write down numbers they want as landmarks
*jumps of any dimension will be taken, jumps of 10 are frequent as a result of it’s a simple psychological computation
*the identical downside can often be solved in a couple of approach on an open quantity line
*it’s a written technique that can ultimately be executed mentally

 

Prerequisite Skills

The cool factor about open quantity strains is that they require (and provides kids observe in) utilizing quantity sense to actually perceive what is occurring when two numbers are added or subtracted fairly than simply crossing numbers out, writing a primary over right here, and doing different steps as a result of your trainer advised you so.  To actually use open quantity strains efficiently, it helps in case your college students have these prerequisite abilities:

open number lines are a powerful strategy for building fluency with adding and subtracting 2-digit numbers, these are the prerequisite skills your students will need to make the most out of this strategy

Smaller numbers to the left, greater numbers to the precise – If college students have had publicity to customary quantity strains, then they are going to in all probability perceive this.  Having a typical quantity line posted someplace in your class is useful for college kids who get confused about this.

Counting by 10s – On an open quantity line, it’s environment friendly to make jumps of 10, fairly than solely jumps of 1.  If your college students can depend by tens ranging from any quantity (each ahead and backward) they are going to be prepared to make jumps of 10 on an open quantity line.  If your kids aren’t fairly there but, here are some quantity sense routines to assist them.

Decomposing numbers – To use an open quantity line, college students will want to have the option to break numbers aside.  At the only stage, they want to have the option to separate the 10s and the 1s in a quantity.  For extra complicated open quantity line methods, they want to each decompose and compose numbers.  For instance, in the issue 49 + 24, it will be environment friendly to break the quantity 24 into 20 + Three + 1 in order that the 1 will be mixed with the 49 to make 50 (a pleasant, pleasant quantity : )

The Concept of “Friendly Numbers” – “Friendly numbers” are simply one other approach of claiming “multiples of 10.”  I clarify to my college students that any time we are able to get to a pleasant quantity it makes our lives a lot simpler as a result of we’re solely coping with 10s, not 1s (“Awww, look how pleasant it’s kids, it doesn’t even have any ones!…ha, ha : )

Combinations that make 10 – This goes hand-in-hand with “pleasant numbers.”  If you realize methods to make 10, then you can also make simpler math issues for your self, you may get your self to a pleasant quantity.  If kids know the combos that make 10, they will take a look at a quantity like 37 and assume, “I would need 3 more to get to the next friendly number because 7 + 3 makes 10.”

 

 

 Addition Strategies

You will discover that there’s a couple of approach to resolve a given downside utilizing open quantity strains.  Some methods are extra environment friendly than others.  These are all out there on a FREE HANDOUT

 

 

Subtraction Strategies

Strategies for teaching addition and subtraction using open number lines, a Common Core 2nd grade math skillStrategies for teaching addition and subtraction using open number lines, a Common Core 2nd grade math skillStrategies for teaching addition and subtraction using open number lines, a Common Core 2nd grade math skill

 

 

Save Yourself Time

If you’re on the lookout for a simple approach to get your kids up and working with open quantity strains, I’ve a useful resource for you in my TpT store.  It begins with a assessment of representing numbers, addition, and subtraction on a typical quantity line, then strikes on to open quantity line fundamentals like making jumps of ten, and continues with extra complicated issues and methods. >>SEE MORE

 

Strategies for teaching addition and subtraction using open number lines, a Common Core 2nd grade math skill

 You can even pattern a few free pages HERE

 

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Hannah Braun

Hannah Braun
Hannah Braun is a former trainer with eight years of expertise within the classroom and a grasp’s diploma in early childhood schooling. She designs partaking, organized classroom resources for 1st-Third grade lecturers.

Author: Hannah Braun

Hannah Braun is a former trainer with eight years of expertise within the classroom and a grasp’s diploma in early childhood schooling. She designs partaking, organized classroom resources for 1st-Third grade lecturers.