Second grade is a very important year when it comes to fact fluency. This is the time when they are learning to become familiar with two-digit addition and subtraction facts. In my previous post, I shared four addition strategies that I focus on Today, I’ll be sharing four subtraction strategies used for introducing 2-digit subtraction.
Just like introducing 2-digit addition, I expose my students to multiple strategies and models they can use to solve subtraction problems. We spend lots of time focusing on WHY something is done before we teach HOW something is done. Giving students choice in their learning by providing them with multiple ways solve problems is helping them succeed. Flexibility is key because every child learns differently.
The Texas TEK for two-digit subtraction states:
2.4B: Add up to four two-digit numbers and subtract two-digit numbers using mental strategies and algorithms based on place value and properties of operations.
The Common Core Standard for two-digit subtraction states:
2.NBT.B.5: Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
Note that the bolded text above says nothing about the standard algorithm we learned growing up years ago. Keep reading to learn about four subtraction strategies I introduce and teach my students when focusing on two-digit subtraction. Also, note that these strategies will not focus on regrouping. Students need a strong understanding of place value AND simple subtraction before moving onto that task.
- Build/draw out the minuend (59) with base ten blocks.
- Take away the amount of the subtrahend (15). Remove 5 ones blocks and 1 tens block.
- Count the remaining blocks left and solve for the difference.
- Expand the minuend. >>> 80+6
- Expand the subtrahend and write it vertically underneath the minuend. >>> 40+3
- Circle the minus sign.
- Subtract and solve vertically based on place value starting with the ones, then the tens.
- Solve for the difference. >>> 40+3=43
- Draw an open number line.
- Write the minuend at the end of the number line. >>> 57
- Determine how many hops and skips you need to take.
- The subtrahend is 27. You need to draw 2 large hops and 6 small skips.
- Skip count backward to solve for the difference.