When the Ones Make Ten or More: Bundling a Brand New Ten

Look for this idea outside of your lessons. Coin counting works this way. Ten pennies become a dime, and the pile changes shape without changing value. This is worth learning because regrouping is the heart of all addition with larger numbers.

Watch for it today, and when you spot it, tell someone what you noticed and how you knew. Ask yourself where else the same idea might be hiding, then go and look.

Let us think about this slowly. Sometimes the ones pile up past ten. Take 27 plus 5. Seven plus five is twelve ones, which is one full ten and two left over. Bundle that new ten and move it over to the tens: now you have three tens and two ones, which is 32.

This is called regrouping. Nothing was added or lost. Ten loose ones simply became one bundle, just like wrapping ten sticks together.

Watch out for the most common error here. Some people write 27 plus 5 equals 212, putting the twelve ones straight onto the page. Twelve ones cannot sit in the ones place. Bundle ten of them and move that bundle where it belongs. Show your work to someone and explain it in your own words.