Reading and writing numbers (age 10+)
Read, write, and compare decimals to thousandths using base-ten numerals, number names, and expanded form; compare using >, =, < based on place-value meaning
What a learner can do afterwards
- Write 347.392 in expanded form: 3×100 + 4×10 + 7×1 + 3×(1/10) + 9×(1/100) + 2×(1/1000)
- Compare 0.372 and 0.38 using place-value reasoning
- Write 'five and sixty-two thousandths' as 5.062
The lesson
You already know tenths and how to compare decimals. Now you will go further, into hundredths and thousandths. Each new place after the decimal point stands for a value ten times smaller than the one before it.
Look at 347.392. The 3 right after the decimal point is 3 tenths, or 0.3. The 9 is 9 hundredths, or 0.09. The 2 is 2 thousandths, or 0.002.
Expanded form adds up the value of every digit: 3x100 + 4x10 + 7x1 + 3x(1/10) + 9x(1/100) + 2x(1/1000) makes 347.392. Word names work the same way. 'And' marks the decimal point, so 'five and sixty-two thousandths' means 5 ones plus 62 thousandths, written as 5.062.
To compare decimals, line up the decimal points and check one place at a time, starting from the biggest place. 0.372 and 0.38 tie at 3 tenths, but 0.38 has 8 hundredths while 0.372 only has 7, so 0.38 is larger.
Read decimals by place value, use 'and' for the decimal point in words, and compare digit by digit starting from the largest place.
Watch it
Where it sits
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.