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Add and Subtract Decimals to Hundredths Using Models and Place Value

Students add and subtract decimals to the hundredths place using concrete models (base-ten blocks, decimal grids) and the strategy of aligning digits by place value. They understand that only like place values can be combined or separated.

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Add and Subtract Decimals to Hundredths Using Models and Place Value

Grade 5 · Decimal Operations · question 1 of 3

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20 rungs. A star at the top.

At the pond, Zoe pours 0.2 gallons of water into a bucket. Then she pours another 0.5 gallons of water into the bucket. How many gallons of water are in the bucket now?

How it is taught

0:00 of 4:55

Line up the decimal points.

Then add or subtract each place.

Read it: Decimals as tenths and hundredths

3.3 + 0.12: line up the points, so tenths sit under tenths. 3.3 has no hundredths, so write it as 3.30. Now count in hundredths: 330 + 12 = 342 hundredths, which is 3.42.

  1. Put the points in one column, so each place sits under the same place.
  2. Write a 0 in any empty place, so both numbers have the same places.
  3. Count both in the smallest place, work as with whole numbers, then write a decimal again.

3.30 is 330 hundredths and 0.12 is 12 hundredths, so the sum is 342 hundredths.

Writing a 0 at the end does not change a decimal: 3.3 and 3.30 are the same number.

10 hundredths make 1 tenth, and 10 tenths make 1 one, so a decimal regroups just as a whole number does.

Points under points, a 0 in every empty place, then work by place as with whole numbers.

Lining up the last digits instead of the points: 0.45.

Line up the points: 3.30 + 0.12 = 3.42.

6.4 + 0.24 = ___ — 6.64. 6.4 is 640 hundredths and 0.24 is 24 hundredths: 664 hundredths, 6.64.

0.36 + 0.47

Imagine you have thirty-six cents, and you find forty-seven more. How much money do you have now?

Let's write it as zero point three six plus zero point four seven. Stack the numbers so the decimal points line up.

This is the most important step — when decimal points line up, place values line up too.

Start at the right, with the hundredths place. What is six plus seven?

Six plus seven is thirteen hundredths.

Thirteen hundredths is one tenth and three hundredths. Write the three in the hundredths place.

Then carry the one over to the tenths column.

Now add the tenths. One plus three plus four.

That's eight tenths. Write the eight.

Bring the decimal point straight down, and the zero in the ones place.

Zero point three six plus zero point four seven is zero point eight three — eighty-three cents. Nicely done!

36¢ + 47¢ = ?$0.36 in your pocket… and $0.47 more!onestenthshundredths0.36+0.47Decimal points line up!6 + 7 = ?6 + 7 = 13= 1 tenth + 3 hundredths311 + 3 + 4 = ?1 + 3 + 4 = 880.Line up the decimals — then add place by place.ANSWER0.83= 83¢
Grade 5 · Lining up place value to add decimals

What you see

While they climb, your page writes one true line to ask about tonight, and a short note each Sunday.

MayaGrade 3 · Mathematics
Did you know?

A chessboard has 64 squares — share them out between the 8 rows and each row holds exactly 8.

Today’s goal
1 star — one skill mastered, every rung of its ladder climbed
Climbing now
Divide within 100

An example student.

MayaGrade 3 · Mathematics

Maya earned 2 stars this week — Interpret multiplication as equal groups, which took 6 answers over 3 days before its star landed 3 days ago and Multiply by 6, 7, 8 and 9. Next up: Divide within 100.

An example week.

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