Texas Math Models

Try “number line” or “4.5D”

The digit rule · the shortcut

4,367 + 2,258 = 6,625 Grade 4

look at the digit to the RIGHT of the place you want nearest hundred 4,367 the 6 in the tens place → 5 or more, round UP ≈ 4,400 nearest thousand the 3 in the hundreds place → less than 5, round DOWN 4,367 ≈ 4,000

How this one works

How

look at the digit just to the right, then round up or down.

Best when

you already know why it works and want to go fast.

The same problem, other ways