You are watching: Show how to make a ten to find 12-4

explain why this reasoning works and also apply this technique to uncover 7 + 8. How deserve to you visualize this equations using the table? adding 9 to another single digit number can additionally be excellent by very first making a 10. For instance

describe why this thinking works and apply this an approach to discover 7+9. How can you visualize these equations using the table?

## IM Commentary

Students are expected to it is in fluent with enhancement and subtraction within 20 in 2nd grade (see 2.OA.2). This job builds ~ above that expertise by questioning them to study more carefully the make-a-ten strategy the they should currently know and use intuitively. In this strategy, understanding of i m sorry sums make a ten, along with some that the properties of enhancement and subtraction, are provided to evaluate sums i m sorry are bigger than 10. The 10"s in the table room shaded due to the fact that they are crucial to the technique. The second part of the task concentrates on including 9"s i beg your pardon can additionally be achieved by including a 10 and also then individually 1. The teacher may wish to suggested to college student for part (b) the showing exactly how to include 9 by very first making a ten through the enhancement table calls for an extra pillar on the table. Alternatively, students have the right to just add one box, v the number 17, to display the amount 7+10. This task is intended for instruction purposes as it takes time to identify the fads involved and also understand the steps in the procedures.

The criter for math Practice focus on the nature the the learning experiences by attending come the thinking processes and habits that mind that students need to construct in bespeak to obtain a deep and also flexible expertise of mathematics. Details tasiilaq.net loan themselves to the demonstration of details practices by students. The methods that room observable throughout exploration that a task rely on exactly how instruction unfolds in the classroom. While that is feasible that tasiilaq.net might be associated to several practices, only one practice connection will be disputed in depth. Feasible secondary exercise connections might be discussed yet not in the same level of detail.Â

This job helps show Mathematical exercise 7, watch for and make usage of structure. Throughout this activity, third graders are actively connecting the strategy of make-a-ten along with properties of enhancement and individually to resolve sums greater than 10. ÂDuring this procedure they are looking at the structure of the base ten system, and also composing and also decomposing numbers based upon this structure.Â college student will have actually the opportunity to think around the an interpretation and usefulness of composing 10s without struggling with the computations which because that a 3rd grader will certainly not be challenging.Â They room asked to visualize this make-a-ten strategy using the enhancement table and explain why this thinking works (MP.3). With this in-depth exploration the the make-a-ten strategy, students are immersed in pattern-recognition and pattern-generalizing which not only establishes a far better understanding the our base ten structure but permits them to use this expertise to solve various other problems.

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## Solution

The an initial equation comes from writing 5 together 2+3. The factor forthis is that in the next step us will group the 2 along with the 8 tomake a 10. This 2nd step provides the associative home of addition. In the 3rd step, we add 10 + 3 to discover theanswer the 13.

In terms of the enhancement table, we deserve to visualize including 5 to 8 bystarting in ~ the 8 in the column of addends and also moving over 5 spacesto the right. Notification that after 2 steps, us reach 10. Then three moresteps puts united state at 13. This is shown in the picture below:

Applying this an approach to calculation 7+8 us find

This technique is comparable to the making a ten method in component (b). In this case,however, a ten is do by rewriting 9 together 10 - 1. Climate the 3 and 10are group together very first before performing the subtraction in the final step.This is shown in the snapshot below: