Video: Adding Tens and Ones on a Blank Number Line

Elizabeth is adding using a number line. Pick the sum she is working on. 28 + 34, 28 + 43, Find the answer.

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Video Transcript

Elizabeth is adding using a number line. Pick the sum she is working on. 28 plus 34 or 28 plus 43. Find the answer.

This question has two parts. First, we need to work out which sum Elizabeth is working on using her number line. Then, we need to find the answer. We need to work out which of these sums Elizabeth is working on. We can see that both of the sums start with number 28. And, Elizabeth starts counting on her number line at number 28. What is she adding to 28? Is she adding 34 or 43?

Let’s take a closer look at the way Elizabeth counted forward on her number line. First, we can see she counted in 10s. Let’s count the number of 10s. There are four 10s. So, the number Elizabeth adds to 28 has four 10s. Then, she added three ones. Elizabeth added four 10s and three ones which is 43. So, the sum Elizabeth is working on is 28 plus 43.

Now, we need to find the answer. What is 28 plus 43? Let’s use Elizabeth’s number line. If we start at 28 and add 10, that will take us to 38. 38 add 10 is 48. 10 more is 58. And, one more 10 takes us to 68. Now, we just need to add the ones. 68 and one is 69. 69 and one is 70. 70 and one is 71. 28 plus 43 equals 71. The sum Elizabeth is working on on her number line is 28 plus 43. And, the answer is 71.

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