Problem-Solving Strategy: Write an Number Sentence Video

Elias and Hudson are best friends. It is Halloween and they are just about to go trick-or-treating. Oh no! Elias’s costume has fallen apart. We need to help Elias and Hudson fix the costume.

There are 20 white buttons and 10 white and blue circles on the ground. These buttons and circles belong on the bottom part of Elias’s costume. How many buttons and circles are there altogether?

Hmmm, we need to add these buttons and circles together, but what should our number sentence be? There are 20 buttons and 10 circles. We can use the addition sentence 20 + 10. Solving addition sentences is simple when we use an addition strategy! Let’s see, we could solve this problem using base ten blocks, a number line, or ten frames.

Let’s use base ten blocks! This is a good idea since 10 and 20 can both be easily represented by base ten blocks.

Here are two groups of ten to represent the number 20, and here is one group of ten to represent the number 10. When we add these base ten blocks, we can think of adding 2 and 1. 2+1=3 groups of ten. We know that 3 groups of ten equals 30.

Great job! Hudson will glue 30 buttons and circles onto Elias’s costume.

These white lines fell off of Elias’s arms. Let’s find out how many lines there are all together so that Hudson can glue them back on.

How many thin, white lines do you see?

Yes! There are 17 thin lines. How many thick, white lines do you see?

Very good! There are 6 thick lines. We can use these numbers to create an addition sentence. Do you know what it is?

That’s right! This is the addition sentence 17 + 6. What addition strategy should we use do solve this equation? Base ten blocks, a number line, or ten frames?

Let’s use the number line! Since 6 is a single-digit number, a number line will be a quick and easy way to add 6 to 17.

Number lines help us see and understand the addends we add together. Begin by circling the largest addend, 17. Now count on by jumping to the right 6 times. This shows 17+6. We landed on the number 23. Great job!

Now Hudson will glue 17 thin lines on Elias’s left arm and 6 thick lines on his right. They are almost ready to go trick-or-treating!

These buttons and levers fell off of Elias’s torso. Let’s find out how many buttons and levers Hudson will glue back on Elias.

Can you create the addition sentence?

Great job! There are 36 buttons and 6 levers. This is the addition sentence 36+6. There is only one addition strategy that we haven’t used today! Let’s add using ten frames!

Ten frames help us add to ten quickly because we can easily group numbers together. Let’s use 36 red dots to represent the 36 buttons and 6 blue dots to represent the 6 levers. First, place the 36 red dots in the ten frames. Then, place the 6 blue dots in the ten frames.

A ten frame holds 10 dots, so if a ten frame is full, we can simply look at it as the number “10”. 40 + 2 = 42. There are 42 buttons and levers all together.

Hudson will glue 42 buttons and levers onto Elias’s costume.

Hooray! Elias’s costume is fixed and now the boys are ready to go trick-or-treating! Thank you for helping them write number sentences and use addition strategies!