Curated OER
Changing Decimals Into Fractions
This simplistic explanation describes how to change a decimal into a fraction. The tutor does a good job explaining that the place value of the decimal determines the number needed in the denominator, but reduces each fraction with out...
Khan Academy
Singapore Math: Grade 3a, Unit 1 (Part 2)
As part of a series on numbers less than 10,000, a thorough presentation demonstrates how to visualize numbers in groups of a thousand. The instructor then describes how to read and write numbers less than 10,000.
Khan Academy
Singapore Math: Grade 3a, Unit 1 (Part 1)
Using a step-by-step approach, Sal from Kahn Academy visually describes what a group of 10, 100, and 1,000 means. It explores the value of numbers less than 10,000. The example is easy to understand. He puts marbles in a can, and the...
Khan Academy
Singapore Math: Grade 3a, Unit 2 (Part 4)
Use the Singapore math methods to work through simple problems. Visual representations of word problems allow viewers to start making predictions and estimating the answers. This is a good way for class members to use various methods to...
Curated OER
How Do You Add Decimals?
Need a review for adding decimals? Make sure to line up the decimals, write in zeros for placeholders, add the numbers, bring down the decimal. There you have it.
Curated OER
How Do You Add Whole Numbers?
Adding whole numbers can be tricky if you don't get all your numbers in alignment. So make sure to get the place value correct.
Khan Academy
Khan Academy: Arithmetic and Pre Algebra: 2 Digit Subtraction
This video shows subtraction of two-digit numbers and place value to tens. [2:54]
Khan Academy
Khan Academy: Arithmetic and Pre Algebra: Addition 2
This video covers addition by counting and using a number line, followed by place value concepts and addition of two-digit numbers. Practice problems are available. [12:26]
Khan Academy
Khan Academy: Arithmetic and Pre Algebra: Decimal Place Value 2
This video shows how to write a decimal in word form, using place value concepts. Practice problems are available. [3:31]
Khan Academy
Khan Academy: Arithmetic and Pre Algebra: Place Value 3
Learn how to write a five-digit whole number in expanded form by watching a video. Practice problems are available. [5:20]
Khan Academy
Khan Academy: Arithmetic and Pre Algebra: Place Value 1
This video teaches place value to the thousands. Practice problems are available. [2:25]
Khan Academy
Khan Academy: Arithmetic and Pre Algebra: Decimals on a Number Line
This video shows how to locate and plot a decimal number on a number line. Practice problems are available. [1:39]
Khan Academy
Khan Academy: Arithmetic and Pre Algebra: Place Value 2
This video shows how to write a number in the hundred millions in standard form from a description. Practice problems are available. [4:09]
Khan Academy
Khan Academy: Arithmetic and Pre Algebra: Decimal Place Value
This video explains place value in decimal numbers. Practice problems are available. [4:00]
Khan Academy
Khan Academy: Place Value Example: 42
Sal shows 42 as 4 tens and 2 ones using a visual demonstration. Includes a video, transcript, and question and answer section. [4:18]
Khan Academy
Khan Academy: Intro to Place Value
Sal uses the number 37 to explain why we use a 'ones place' and a 'tens place' when writing numbers. Includes a video, transcript, and question and answer section. [5:58]
Khan Academy
Khan Academy: Comparing Whole Numbers
Sal compares 394 and 397 and then writes the expression using < or >. Includes a video, transcript, and question and answer section. [2:04]
Khan Academy
Khan Academy: Place Value Example: 25
Sal shows 25 as 2 tens and 5 ones using a visual demonstration. Includes a video, transcript, and question and answer section. [2:54]
Khan Academy
Khan Academy: Teens as Sums With 10
Sal looks at the 1 in each teen number and thinks about what it really means. Includes a video, transcript, and question and answer section. [2:59]
Khan Academy
Khan Academy: Teen Numbers: Monkeys
Sal breaks the number 18 into 10 and 8 using monkeys. Includes a video, transcript, and question and answer section. [2:57]
Khan Academy
Khan Academy: Subtracting 3 Digit Numbers (No Regrouping)
Sal shows how to subtract 357-251 (without regrouping) using place value. Includes a video, transcript, and question and answer section. [2:56]
Khan Academy
Khan Academy: Subtracting 1s, 10s, and 100s
Sal demonstrates visually how to subtract 3-digit numbers by subtracting ones, tens, and hundreds. Includes a video, transcript, and question and answer section. [3:11]
Khan Academy
Khan Academy: Solving 3 Digit Addition in Your Head
Sal shows some techniques for doing mental addition, such as making groups of 10 and 100. Includes a video, transcript, and question and answer section. [7:27]
Khan Academy
Khan Academy: Addition Using Groups of 10 and 100
Sal rewrites three-digit addition problems to make them easier to solve. Includes a video, transcript, and question and answer section. [3:57]