lesson
Updated 1 month ago · 7 views
Imagine you are playing an arcade game with a score of 240, and you grab a power coin worth 10 points.
Your score flips to 250 instantly — but why did only one digit move?
The Tens Place
Every three-digit number has three spots: hundreds, tens, and ones.
When you add 10 or subtract 10, you are changing the amount in the tens place by exactly 1.
Having a place value focus means understanding that adding or subtracting 10 (n±10) primarily changes the tens digit while leaving the ones digit invariant (unchanged).
You can use mental decomposition to break a number into parts, like 468=400+60+8.
To find 10 more, add 1 ten to the tens place (60+10=70⟹478). To find 10 less, subtract 1 ten (60−10=50⟹458).
📊A visual place value chart comparing three numbers side by side: 332, 342, and 352. Show base-ten representations (flats for hundreds, rods for tens, small cubes for ones). In the center card for 342: highlight 4 blue rods in the tens column. Left card shows '10 Less' with 3 rods (332). Right card shows '10 More' with 5 rods (352). Bold text labels show that the hundreds (3) and ones (2) stay green, while the tens digit changes (3, 4, 5). Responsive, clean white card layout with blue accents.
For 342+10, you add 1 ten to the 4 tens to get 5 tens, making the number 352.
For 342−10, you take 1 ten away from the 4 tens to get 3 tens, making the number 332.
That works smoothly when the tens digit is between 1 and 8 — but what happens when the tens place already has a 9?