Video: Identifying Mistakes in Solutions to Word Problems Requiring Addition or Subtraction

Emma is trying to solve this word problem. There were 41 birds in a tree. 15 of them flew away. How many birds are in the tree now? Emma said the answer was 41 + 15 = 56. What did she do wrong? What is the correct answer?

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Video Transcript

Emma is trying to solve this word problem. There were 41 birds in a tree. 15 of them flew away. How many birds are in the tree now? Emma said the answer was 41 plus 15 equals 56. What did she do wrong? What is the correct answer?

We can use a bar model to help us picture the problem. We know there were 41 birds in the tree. 15 of them flew away. We need to work out how many birds are left. To find out how many birds are left, we start with 41 and we need to subtract 15. We could partition 15 into a 10 and a five. First, we can take away 10 from 41, which is 31. Then, we can take away five from 31, 30, 29, 28, 27, 26. So, 41 take away 15 is 26.

What did Emma do wrong? What is the correct answer? Emma added to find her answer. She calculated 41 plus 15 equals 56. So, she added when she should have subtracted. The answer is 41 take away 15 equals 26. We used our bar model to help us picture the problem. We had 41 birds. 15 flew away. There are 26 birds in the tree now. To find the answer, we subtracted.

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