At the beginning of the semester I made the choice to follow the mathematical development of G. a second-grade student at McKinley Elementary School. G. was identified as performing below grade level at the beginning of the semester. At the time, he was comfortable performing addition of values less than ten. Since that time he has come a long way, and is now adding and subtracting multi-digit numbers with some success. To assess how far he has come, I utilized problems from Children's Mathematics, Cognitively Guided Instruction and Extending Children's Mathematics, Fractions and Decimals, Innovations in Cognitively Guided Instruction.
Robin had 6 toy cars. Her parents gave her 8 more toy cars for her birthday. How many toy cars does she have now?
G.'s thinking on this problem shows that he is able to add two single digit numbers. His chosen strategy is consistent with a pencil and paper direct modeling strategy, as defined by Carpenter, Fennema, Franke, Levi, and Empson (2015). After drawing his chart and counting the one's present in the problem, I asked him about bundling. We had covered bundling as a class and G. typically bundles when adding multi-digit numbers. G. circled ten on the small dots in the one's place on his chart. This tells me that G. understands bundling but does not use it as a strategy.
Robin had 6 toy cars. Her parents gave her some more toy cars for her birthday. Then she had 20 toy cars. How many toy cars did Robin get for her birthday?
G. was not successful in solving this join change unknown problem. Instead of finding the number of toy cars Robin received, G. found the sum of the two values in the problem. The misconception seems to lie in G.'s comprehension of what the problem was asking. Upon reviewing the recording, I believe I could have done more to facilitate his understanding of the problem. At the time, I did not assist G. in comprehending the problem because I wanted to see what he can do. His inability to comprehend the problem makes me wonder about the rest of the class's ability to comprehend join change unknown problems.
Robing had some toy cars. Her parents gave her 16 more for her birthday. Now she has 28 cars. How many cars did Robin have before her birthday?
G. also had a difficult time with this join start unknown problem. He approached the problem using an equation, which he set up correctly. He then attempted to use the tape diagram strategy he learned this year, per the Engage New York mathematics curriculum. As can be seen in G.'s work, he does not fully understand how to use tape diagram. When used correctly, a tape diagram illustrates the relationships present in the problem; making it easy for students to intuitively understand how to solve the problem. For example, a tape diagram for this problem would look similar to G.'s but have 28 in the large tape strip, and the question mark in one of the bottom tape strips. G. puzzles over the incorrectly set up tape diagram for a while before admitting he was stuck.
He next attempted to solve the problem with a direct modeling strategy. In the recording G. can be heard asking about using blocks to solve the problem. When he could not find enough blocks, I asked him to draw what he would do with the blocks. Drawing the little squares took a significant amount of time. Then G. had to decide how to take out the 16 cars Robin got for her birthday. To do this, G. chose to erase 16 squares. However, he did not count the squares before he started erasing. When he realized he had erased too many, he stated the remaining squares were the solution instead of recalculating what he had done.
While it was initially clear G. comprehended what was occurring in the story problem, he had a difficult time arriving at a solution. The class will be covering subtraction more in depth in the next couple weeks, which should help G. solve problems similar to this one.
Sally had 13 pencils. She gave 4 pencils to Fred. How many pencils does Sally have now?
This separate result unknown problem was easy for G. to solve. He utilized a direct modeling strategy, which entailed drawing squares for the initial 13 pencils and then crossing off 4 squares to symbolize the pencils given to Fred. However, as G. is in second-grade, he should no longer rely on direct modeling for subtraction problems less than 20. This work is an improvement from where G. was at the beginning of the semester, but he is still not performing at grade level.
Tom had 13 pencils. He gave some pencils to Same. Then he had 4 pencils left. How many pencils did Tom give Sam?
This problem was also easy for G. to solve. For this problem, G. connected the relationships in the story problem to the relationships in the previous problem. G. noted the problems contained the same values, which allowed him to use the work that he had already completed.
Mrs. Hammond had some pencils. She gave 25 pencils to her class. Then she had 63 pencils left. How many pencils did Mrs. Hammond start with?
I was amazed at how quickly G. solved this problem. Especially considering he solved it mentally. However, his explanation of his solution did not make any sense. It is clear G. added the numbers together by place value, thus arriving at the correct solution. When he explains what he did, he talks about subtraction. He also states he is sure it is subtraction. Even though I was not able to understand his explanation, I chose to praise G. for using mental math to solve the problem. I have been trying to develop a growth mindset in G. since the beginning of the semester, and while G.'s confidence has grown, he is still surprised when he is successful at mathematics.
13 boys and 18 girls were on the bus to go to the zoo. How many students were going to the zoo?
67 people were in line to buy movie tickets. 22 were girls and the rest were boys. How many boys were in line to buy tickets?
Bob has 7 dogs. Joe has 13 dogs. Joe has how many more dogs than Bob?
The cat has 13 toys. The dog has 17 more toys than the cat. How many toys does the dog have?
Joy has 12 mice. She has 4 more mice than Mark. How many mice does Mark have?
13 + 29 = _______
98 - 39 = ________
17 + _____ = 63
49 - _____ = 14
_____ + 23 = 62
_____ - 17 = 59
Megan has 10 bags of cookies with 4 cookies in each bag. How many cookies does Megan have?
Spider man caught 24 bad guys. He put them in 4 jails with the same number of bad guys in each jail. How many bad guys did Spider man put in each jail?
Santa made 15 presents. He put 3 presents in each box. How many boxes can Santa fill?
Carpenter, T.P., Fennema, E., Franke, M.L., Levi, L., & Empson, S.B. (2015). Children’s mathematics, Cognitively guided instruction (2nd ed.). Portsmouth, NH: Heinemann.
New York State Education Department (2014). Grade 2 mathematics. Retrieved from https://www.engageny.org/resource/grade-2-mathematics