Challenge 4

The students progressed with their addition and subtraction between interviews, especially learning their doubles, fives, and tens. All four students seemed to use these three skills often, especially when working with larger numbers.

Derek: When solving 5+4, he said he knew that 4 is one less than 5, so he just doubled 5 and took away 1. Derek always gets the right answer to the questions, but his explanations are long-winded and confusing. He works very well with his doubles.

Elizabeth: For the questions that Elizabeth doesn't know immediately, she solves them by using her fingers. For 11-7, she says she pretended there was one more finger, then took away 7. She got confused, though, and ended up with 3. When solving 9+6, she said immediately that the answer was 15 because 10+6=16, so 9+6=15. She is good with logic, and she uses her tens, fives, and doubles whenever possible.

Jim: Jim uses dominos when subtracting, flipping them over as he counts down. He also uses his tens, fives, and doubles. For 15-7, he knew that 7+7=14, and one more is 15, so 1+7=8. I thought his thinking process for solving 7+6 was more complex. He took the 6 and broke it into 3 and 3, then added one 3 to the 7 to make an even 10. Then he had 3 left over, and 10+3=13. His logic is present, but he also changed his answers multiple times, either because he didn't know or because he solved the problem quickly and made a careless mistake.

Lauren: She was very good at addition and subtraction before the elapsed time, but now she always gets the right answer. For 8+9, Lauren took 1 away from the 8 and added it to the 9 to make 10, then added the remaining 7 to get 17. For 12-4, she used her fingers. She pictured 2 imaginary fingers that she immediately took away, then she took away 2 real fingers to give her the answer of 8.

All four children gained logic and problem-solving skills throughout this elapsed time. They all learned to use their finger less and use easy numbers (5 and 10) whenever possible.