Becoming comfortable with two-digit and three-digit numbers is an important skill in second grade. Your child will master addition and subtraction problems within one-thousand. But, how your child learns to understand addition and subtraction is very important.
Here’s how you can help.
One-hundred seventy six plus forty-five. How do we solve this? Let’s make a helpful place value chart! We will break each number into hundreds, tens, and ones, and represent them in each column.
One-hundred seventy six is made up of one hundred, seven tens, and six ones. In forty-five, there are no hundreds, four tens, and five ones.
First, we add the ones together. Six ones plus five ones is eleven ones. If there are ten or more ones, than we bundle. Do you know how to bundle? Your child knows to bundle ten ones together to make one ten. Now, we have one one left.
Next, we add the tens. Seven tens plus five tens is twelve tens. So, we bundle again! A bundle of ten tens make one hundred. How many tens are left? Two!
Last, we add up the hundreds. One hundred, two hundred. There are two hundreds. Do we need to make a bundle? Nope!
Look! We just showed why one-hundred seventy six plus forty-five equals two-hundred twenty-one!
If you look closely, a place value chart is a helpful tool to use before your child uses the standard algorithm. The place value chart teaches your child why the standard algorithm works. How powerful!
And that’s good to know.
Common Core Grade 2 Standard Number & Operations in Base Ten
(2.NBT.1) Understand that the three digits of a three-digit number represent amounts of hundreds, tens, and one; e.g., 706 equals 7 hundreds, 0 tens, and 6 ones. Understand the following special cases: a) 100 can be thought of as a bundle of ten tens – called a “hundred.”
(2.NBT.5) Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.