AAAMath.com
Sorted by Grade Level
Contact AAA Math Contact AAA Math      Contact AAA Math Buy the AAA Math CD      AAA Math en Español Spanish version

Sorted by Subject

Addition with Mental MathLearn LearnTable of Contents Table of Contents
Practice PracticeNext Lesson Next Lesson
Play PlayPrevious Lesson Previous Lesson
Explore Explore Feedback Feedback

Practice Your Spelling List

States of the United States

Nations of the World

 

Mentally Adding Two-Digit Numbers

How to mentally add two two-digit numbers.

  • Add 84 and 35.
  • First add the two ones' place digits (4 + 5 = 9).
  • Next add the two tens' place digits (8 + 3 = 11).
  • The sum of the ones' place digits is less than ten so the answer is 119
  •  
  • Add 94 and 67.
  • First add the two ones' place digits (4 + 7 = 11).
  • Next add the two tens' place digits (9 + 6 = 15).
  • The sum of the ones' place digits is a two-digit number so
    • decrease the ones' place sum by 10 (11 - 10 = 1)
    • increase the tens' place sum by 1 (15 + 1 = 16)
  • Combine the tens' and ones' place sums to give the answer of 161

Another method to mentally add two two-digit numbers may be easier in some situations.

  • Add 84 and 35.
  • First add the two tens' place digits (8 + 3 = 11).
  • Next add the two ones' place digits (4 + 5 = 9).
  • The sum of the ones' place digits is less than ten so the answer is 119.
  •  
  • Add 94 and 67.
  • First add the two tens' place digits (9 + 6 = 15).
  • Next add the two ones' place digits (4 + 7 = 11).
  • The sum of the ones' place digits is more than nine so:
    • Decrease the ones' place sum by 10 (11 - 10 = 1.)
    • Increase the tens' place sum by 1 (15 + 1 = 16).
  • Combine the tens' and ones' place sums to give the answer of 161





Find the Sum of the two Numbers.

  +     =     


You have correct and   incorrect.  This is percent correct.

Return to Top


Play
PlayGameWhat is it?Best Score
How many correct answers can you get in 60 seconds?
Extra time is awarded for each correct answer. Play longer by getting more correct.
How fast can you get 20 more correct answers than wrong answers?

Sudoku

Timez Attack Multiplication Video Game

Return to Top

Math Lessons by Grade
Math Topics

Math Resources

Spelling Lessons by Grade

Vocabulary Lessons by Grade

Geography

WorldPlenty.com

Other Interests

Return to Top



Copyright © 2009 J. Banfill. All Rights Reserved. Legal Notice

Copyright (C) 2009 J. Banfill. All Rights Reserved.