Making one addend the next tens number is a mental math strategy that turns a tricky addition problem into an easier one by adjusting one number up to the nearest multiple of ten and balancing the change in the other addend. The new problem becomes 40 + 45 = 85. Take this: instead of calculating 38 + 47 directly, you can make 38 the next tens number, 40, by adding 2, then subtract 2 from 47 to keep the total unchanged. This approach builds number sense, speeds up mental calculation, and helps students understand why numbers can be rearranged without changing their sum It's one of those things that adds up..
What Does It Mean to Make an Addend the Next Tens Number?
An addend is any number being added in an addition problem. Day to day, the next tens number is the multiple of ten that comes next after a given number. In 28 + 37, the addends are 28 and 37. The next tens number after 28 is 30; after 37, it is 40; after 84, it is 90.
The strategy works because addition is flexible. That said, if you increase one addend by a certain amount, you must decrease the other addend by the same amount to keep the total the same. This is often called compensation Most people skip this — try not to..
- If A + B = C,
- then (A + k) + (B − k) = C.
You are not changing the value of the expression. You are only reshaping it into a form that is easier to compute.
Why This Strategy Is Useful
Many students can add multiples of ten quickly: 20 + 30, 40 + 50, 70 + 20. Here's the thing — the difficulty usually appears when both addends contain ones digits that require carrying or careful counting. Making one addend the next tens number removes that friction.
Here's a good example: 57 + 26 can feel messy because 7 + 6 requires regrouping. But if you make 57 the next tens number, 60, by adding 3, you subtract 3 from 26 to get 23. Now the problem is 60 + 23 = 83. The ones digit in the first addend is zero, so the addition is much cleaner.
This strategy also strengthens place value understanding. Students see that 57 is only 3 away from 60, and that moving those 3 units from one addend to the other preserves the total. That kind of reasoning is more valuable than memorizing a procedure alone.
Step-by-Step Method
Step 1: Identify the addend you want to adjust
Look at both addends and choose
