Decimals to three places
Solve problems involving numbers with up to three decimal places
What a learner can do afterwards
- Calculate the total of three measurements: 1.234 m + 0.567 m + 2.199 m
- A bottle holds 1.5 litres; 0.375 l is poured out — how much remains?
- Find two numbers with 3 d.p. that add to make 1
The lesson
Numbers like 1.234 have three digits after the decimal point: tenths, hundredths, and thousandths. You already know how to compare these numbers. Now you'll add and subtract them, just like whole numbers, but the decimal points must line up first.
Add 1.234 m, 0.567 m, and 2.199 m. Line up the decimal points so tenths sit under tenths, hundredths under hundredths, and thousandths under thousandths. Adding column by column gives 4.000 m exactly, with nothing left over.
Numbers don't need the same number of decimal digits to add or subtract. Write 1.5 as 1.500 first, so every column lines up with numbers like 0.375 or 2.199.
Line up the decimal points, padding with zeros if needed, then add or subtract column by column.
Watch it
Where it sits
This opens up
Nothing builds on it yet.
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.