Texas Math Models

Try “number line” or “4.5D”

Standard algorithm

2.45 + 1.8 = 4.25 Grade 4

line up the DECIMAL POINTS, not the right-hand digits addingsubtracting 1 2.45 1.8 0 + 4.25 4 tenths + 8 tenths = 12 tenths → carry 1 WHOLE the 1 sits over the ones: the point is not a column 3 1 4.25 1.8 0 − 2.45 2 tenths cannot give 8: trade 1 whole for 10 tenths 4 becomes 3 · the tenths become 12 · 12 − 8 = 4

How this one works

How

stack the numbers so the decimal points line up, then add or subtract.

Best when

you want the quickest way.

seen one of these on a test? See it on a real question: TEKS 4.4A, adding and subtracting decimals, or TEKS 4.2G, decimals and fractions that mean the same thing.

The same problem, other ways