Video: Finding the Total Number of Objects by Counting and Identifying the Related Addition Sentence

Ethan bought 5 blue pens and 2 green pens. How many pens does he have in total? Find the matching number sentence. [A] 3 + 5 = 8 [B] 5 + 2 = 7 [C] 5 + 2 = 6 [D] 5 + 4 = 9

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Video Transcript

Ethan bought five blue pens and two green pens. How many pens does he have in total? Find the matching number sentence. Three plus five equals eight, five plus two equals seven, five plus two equals six, or five plus four equals nine.

Let’s take our time and read through this word problem again. Ethan bought five blue pens and two green pens. Let’s underline these two amounts; they’re going to come in useful later on. The question continues, how many pens does he have in total? And we know, of course, that that word “total” means that we’re going to have to add to find the answer. We need to find how many pens Ethan has altogether. This is an addition word problem. We’re putting two groups of objects together. Let’s model the problem. We could use a part–whole model using counters. Five blue counters to represent Ethan’s five blue pens. And we can use two green counters to represent his two green pens.

And the question is asking us, how many counters are we going to need to put in this top circle of our part–whole model? In other words, how many pens did Ethan have in total? Let’s move our counters one by one into that top circle. And we’ll count them as we do. Altogether, Ethan is going to have one, two, three, four, five, six, seven pens. We solved the word problem by modeling it using counters. Five blue pens plus another two green pens makes seven pens in total. We can also show our word problem as a number sentence.

And in the second part of the question, we’re asked to find the matching number sentence. Which number sentence shows us that five blue pens and two green pens makes a total of seven pens? Well, it’s this one here, isn’t it? Ethan has seven pens in total. And the matching number sentence is five plus two equals seven.

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