February also brings us Valentine's Day. We will celebrate the day of friendship on Thursday, February 14. Information already went home about that. A parent has already volunteered to provide paper goods and juice boxes -- THANK YOU!
President's Day is also an important part of February. We will only get a glimpse of Washington and Lincoln's lives before the holiday. After vacation (and after we wrap up our current science unit on the sun, moon, Earth, weather and water cycle) we will do a more in depth study of Washington, Lincoln, the US Constitution, and other ideas related to government. We will also use that time to explore (and create) biographies.
Currently in math we have completed our unit in number patterns and ratios, and are now back to addition and subtraction story problems. Students are looking at numbers in terms of ones, tens, and sometimes hundreds in order to break apart - and put back together - numbers for the purpose of addition or subtraction. This is also a good strategy for mental math, as it is difficult to regroup ("borrow" or "carry") in your head. Here are some examples of breaking numbers in tens and ones:
56 + 32=
50 + 6 + 30 + 2
50 + 30 = 80
6 + 2 = 8
80 + 8 = 88
SO.... 56 + 32 = 88
47 + 25 =
40 + 7 +20 + 5
40 + 20 = 60
7 + 5 = 12 (which is 10 + 2)
60 + 10 + 2 = 72
SO...47 + 25 = 72
(This one would require regrouping - or "carrying" - when doing the algorithm.)
74 - 31
70 - 30 = 40
4 - 1 = 3
40 + 3 = 43
SO... 74 - 31 = 43
52 - 38 =
This one needs to be thought of in a different way, because you cannot take 8 away from 2 for this problem. When students do not have a firm understanding of the number system, they will try to take 2 away from 8.
Here is one strategy that most second grade students find helpful (it is also how I would solve this in my head):
38 is 2 away from 40, so I will think "52-40," which is like going AWAY from 52 two more spaces on a number line.
52 - 40 =
50 - 40 = 10
2 - 0 = 2
10 + 2 = 12
BUT... 12 is not the final answer! Remember, I ADDED 2 in the beginning, so now I need to ADD that 2 back into my difference:
12 + 2 = 14
SO... 52 - 38 = 14
Now, I know that this written explanation looks and sounds a little confusing. Even I questioned myself as I wrote it, and I do this all the time! The important thing to remember is that if your child has a strategy that works for him/her, and they understand it and can explain it, then it's good. Some students still use pictures, some students use pictures that look like tens and ones (5 tens rectangles, and 2 single squares to represent 52), and some are able to easily manipulate the numbers in terms of tens and ones without pictures. Having this understanding of how numbers combine, shift, and break apart will support their understanding of algorithm use in later years.
Students in my class also hear over and over the importance of the PROCESS and the THINKING over just getting an answer. My calculator can give me an answer - I am much more interested in how a second grade student is thinking about a problem, and WHY their strategy worked!
ALSO -- I have some pages to copy and send home that can better illustrate the strategies that we are working on. It is so much easier to explain with other lines and drawings - functions that I have yet to master in this blog format!
In other news: Students have been working on writing Friendly Letters in Writing Workshop. The parts of a Friendly Letter include: the date, greeting, body with an interesting topic and details, closing, and signature. Students have used a checklist to self-evaluate their ability to write a Friendly Letter. Once these letters are checked by me, and fixed up by them, students will be able to bring them home. Some students will want your help to actually mail their final letter!
