In this video, Mahalo math expert Allison Moffett shows you how to do double-digit addition.
Step 1
To add two double-digit numbers like 77 and 29 together, start by rewriting the problem vertically so that the ones column lines up and the tens column lines up as well.
Step 2
Add the ones column together. Since 9+7=16, take the ones digit of the sum (6) and write it in the ones column below the sum line.
Step 3
Take the tens digit (1) and carry it over the top of the tens column. Add the 7, 2 and 1 together (7+2+1=10).
Step 4
Since there are no more columns to add, write the 10 as a whole digit below the tens column. Your answer is 106.
References
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Introduction to Numbers 5:45
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Classification of Numbers 12:48
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An Introduction to Whole Numbers 0:00
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Whole Numbers and Place Value 0:00
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Prime and Composite Numbers 2:54
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Definition of Rational Numbers 2:49
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What is Expanded Form? 0:00
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Rewrite Numbers in Expanded Form with Exponen... 0:00
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The Mean, Median and Mode 4:23
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Word Problem: Identifying Integers (Level 1) 0:48
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Word Problem: Identifying Integers (Level 3) 1:00
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Quiz: Whole Numbers into Expanded Form 0:54
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Basic Mathematical Functions 20:54
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Fundamental Theorem of Arithmetic 4:09
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Single Digit Addition and Subtraction 2:28
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Double Digit Addition 0:00
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Double Digit Subtraction 0:00
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Basic Multiplication 2:18
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The Lattice Method of Multiplication 0:00
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Making Decimal Multiplication Easier 2:15
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How to Do Long Division 0:00
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Tests for Divisibility 7:30
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How to Calculate Your Gas Mileage 0:00
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Two Trains Word Problem 1:03
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Gold Coins Brain Teaser 1:11
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Quiz: Finding Interest 0:00
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Numbers and Factors 31:09
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Prime Factorization 7:03
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Factoring Whole Numbers 0:00
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How to Find a Common Denominator 5:25
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Greatest Common Factor (GCF) 4:56
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Lowest Common Multiple (LCM) 5:24
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Finding the GCF and LCM 3:13
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Alternative Methods for Solving GCF and LCM 1:46
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The GCF-LCM Product Theorem 3:22
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Quiz: Factoring Whole Numbers 0:00
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Mixed Numbers and Fractions 7:29
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Fractions as Parts of a Whole 0:00
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How to Notate Fractions 0:00
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How to Convert Mixed Numbers into Fractions 1:22
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How to Convert Fractions into Mixed Numbers 0:00
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How to Convert Fractions into Decimals 2:15
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How To Reduce Fractions 0:00
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How to Add Fractions 0:00
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How to Subtract Fractions 1:53
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How to Multiply Fractions 0:00
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How to Divide Fractions 0:00
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How to Add or Subtract Mixed Numbers 0:00
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How to Multiply Mixed Numbers 0:00
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How to Divide Mixed Numbers 0:00
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Word Problem: Fractions and Proportions 1:07
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Word Problem: Elmo the Painter 0:52
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Quiz: Mixed Numbers 0:00
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Decimals and Radicals 0:53
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An Introduction to Decimals 0:00
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Ordering Decimals 0:00
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How to Write a Decimal in Expanded Form 0:00
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How to Write Decimals in Scientific Notation 0:00
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How to Convert Percents to Decimals 0:00
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How to Divide Decimals 0:00
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How to Divide Decimals in the Dividend 0:00
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How to Add Radicals 0:00
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How to Simplify Radicals 0:00
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Quiz: Decimals into Expanded Form 0:53
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Quiz: Convert Fractions to Decimals 0:00
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Quiz: Convert Decimals to Fractions 0:00
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Percentages 17:21
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Mathematical Properties of Numbers 2:10
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Order of Operations 2:08
Meet Our Experts
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Allison Moffett
Mahalo math expert Allison Moffett holds a bachelor's degree in physics from the University of California, San Diego and a master's degree in mathematics from San Diego State University. She has spent years working as a math teacher and enjoys breaking down often complex processes into easily understandable and repeatable steps.
More Than Two Digits
The same rules apply as for double digits, but you must make sure that when you line up your numbers vertically, only the ones get added to the ones, the tens to the tens, the hundreds to the hundreds, etc.
