Add 2-digit Numbers — Grade 4

When introducing 2-digit addition, begin with concrete examples. Use base-10 blocks or place value charts to show a problem like 46 + 89. Show 4 tens and 6 ones, then add 8 tens and 9 ones. Count the tens: 4 + 8 = 12 tens (120). Count the ones: 6 + 9 = 15 ones, which is 1 ten and 5 ones. So you have 12 tens + 1 ten + 5 ones = 13 tens + 5 ones = 135. This concrete experience helps students understand place value and regrouping.

Next, introduce the breaking apart strategy. Show how 46 + 89 can be thought of as (40 + 6) + (80 + 9) = (40 + 80) + (6 + 9) = 120 + 15 = 135. Emphasize that 15 ones equals 1 ten and 5 ones, so 120 + 10 + 5 = 135. Use number lines to visualize this: start at 46, jump 89, land on 135. Practice this repeatedly with different number combinations.

As students become comfortable, introduce mental strategies. Teach them to recognize when carrying is needed (when ones add up to 10 or more) and how to handle it efficiently. For example, 46 + 89: think 40 + 80 = 120, 6 + 9 = 15, so 120 + 15 = 135.

Finally, encourage students to check their answers by using subtraction or by breaking numbers apart differently. This self-checking habit builds confidence and reinforces place value understanding.