Eureka Math Grade 2: Compensation in Subtraction

Eureka Math is Not Your Parents’ Math.

It’s the scratch your head, not in my day, kind of math.

I’d like to make it easier!

This year, I am back in 2nd grade teach­ing an entire cur­ricu­lum after spend­ing the last five years as a high school Inten­sive Read­ing teacher. So, I was return­ing to my roots. My first four years as a teacher were spent in pri­ma­ry. The math cur­ricu­lum, Eure­ka Math, was rolled out this year, and it was very dif­fer­ent than any­thing I had ever seen.

Changes that Make Me Ask “Why?”

In some areas, the changes were strange, and in my opin­ion, unnec­es­sary. For exam­ple, the num­ber you nor­mal­ly car­ry when you add became a “num­ber below” which is where you put it when you bun­dled a group of ten.

Changes that Make Me Say “Eureka!”

In many oth­er ways, I have grown to love the pro­gram. It is com­plex and forces stu­dents to think like a math­e­mati­cian. The lan­guage of math is more present in my class than it has ever been. As we solve algo­rithms, 2nd grade stu­dents prac­tice a vari­ety of strate­gies right from the begin­ning. Now that we have reached the halfway point in the year, stu­dents can have con­ver­sa­tions about their favorite strate­gies and cri­tique oth­ers’ errors.

Some strate­gies are more dif­fi­cult than oth­ers. One such strat­e­gy has been giv­ing my stu­dents par­tic­u­lar trou­ble. It involves using com­pen­sa­tion to sim­pli­fy equa­tions so that stu­dents can even­tu­al­ly solve these prob­lems quick­ly and accu­rate­ly in their head.

Using Compensation in Subtraction

Stu­dents are taught to use tape dia­grams to sep­a­rate the two val­ues in the sub­trac­tion prob­lem. 
They will add or sub­tract the same num­ber from both to get an eas­i­er “in your head” equa­tion. For exam­ple, 372–198 would become 374–200 by adding 2 to both numbers.
Stu­dents can solve the sec­ond equa­tion faster and more accurately.

What I find incred­i­ble is how I have tran­si­tioned to using these Eure­ka math strate­gies in my own life!

Any­way, because my stu­dents were strug­gling with this con­cept, I cre­at­ed a “stu­dent-friend­ly” activ­i­ty to help them to mas­tery. I want­ed them to be able to work on it alone and still have it make sense.

Here is the TPT activ­i­ty for using com­pen­sa­tion for sub­trac­tion I made for my students.

I would love to hear how you are over­com­ing obsta­cles with­in your cur­ricu­lum. What’s work­ing for you?