Materials & Prep
- Four base-ten block sets, each with tens rods and ones cubes.
- Board or chart with a labeled Tens | Ones place-value mat and the problem 28 + 15.
- Give each pair a small dry-erase board or paper and pencil. Post three practice problems: 36 + 27, 47 + 16, 58 + 25.
Gather and model
Ask“I have 8 single cubes and get 5 more. How could we organize them so they are easy to count?” Let children turn and talk, then have a few show 13 ones. Connect: “We already know that 10 ones can be traded for 1 ten. Today that same trade helps us add bigger numbers.”
DisplayBuild 28 as 2 tens rods and 8 ones cubes, and 15 as 1 tens rod and 5 ones cubes in the Tens | Ones mat. Have students say what each rod and cube represents.
Think aloud“I start with ones because I have 8 ones and 5 ones. That makes 13 ones. I cannot leave ten loose ones in the ones place. I trade exactly 10 ones for 1 tens rod, leaving 3 ones. Now I have 2 tens, plus 1 ten, plus the new ten from my trade: 4 tens. The sum is 43.” Write the vertical equation as the blocks are traded: 28 + 15 = 43.
MisconceptionPoint to the incorrect answer 313. “Someone added 8 + 5 and wrote 13, then added 2 + 1 and wrote 3. Does 313 match our blocks?” Students signal thumbs down and explain that 13 means 1 ten and 3 ones, not “13 ones beside 3 tens.” Cross out 313 and match 43 to 4 tens and 3 ones.
Check for understandingShow 26 + 18. Ask children to hold up fingers for how many ones are made, then ask, “What can 14 ones trade for, and what stays in the ones place?” Listen for “one ten and four ones.”
Partner practice
TransitionPartners move to a marked space with their board. Four assigned pairs begin at the block table; remaining pairs begin by drawing tens sticks and ones dots in a place-value mat. After 8 minutes, switch.
Have students solve 36 + 27 together. Partner A builds or draws 36 and Partner B builds or draws 27. Both combine ones, circle 10 ones, draw or trade for a new ten, then count tens and ones. Partners say the complete sentence: “ ones make ten and ones, so 36 + 27 = .”
CirculateAsk, “Where did this extra ten come from?” and “How do your drawing and number match?” Watch for children writing 313-style answers or counting the ten twice. Have them physically point to the traded group of 10 and the new tens rod.
ScaffoldKeep the Tens | Ones mat visible. For children who need a defined entry point, say, “Build the ones first. Touch and count them. Make a circle around 10. Trade that circle for one tens rod.” Pair them with a partner who states each trade aloud.
ExtensionWhen a pair finishes accurately, give 58 + 25 without blocks. Challenge them to solve mentally by saying the trade: “8 plus 5 is 13, so I make one more ten,” then justify why their answer is 83. Ask them to create a different two-digit addition problem with an answer of 83 that requires a trade.
Math workshop
StudentsEach pair chooses one of the posted problems, 47 + 16 or 58 + 25, and solves it on its board using blocks, a quick drawing, or numbers. Both partners must be ready to explain the regrouping.
Check for understandingVisit each pair and ask one child, “How many ones did you have before the trade?” Ask the other, “How many tens do you have after the trade?” Record who can connect the trade to the written sum. Prompt a correction before partners erase.
Come back together
Show me: Display 39 + 14. Children quietly solve with fingers or a board, then show their answer together. Call on one child to explain what happened to 9 ones plus 4 ones.
Expected“Thirteen ones trade for one ten and three ones. Three tens plus one ten plus the traded ten makes five tens, so the answer is 53.”
Chant: “Ten ones make a ten. Trade, then count the tens again.”