Today is . WELCOME: wang--/44447  Home | Reg LoginAll user | setHomePage | Bookmark  
Home | Math Test Online | Addition | Subtraction | Multiplication | Division | Time | Worksheet(JPG/PDF) | CAI | Flash Games | 
 Recommendation article
 Article search
 
 Home--maths--Third Grade--Mentally Adding Two-Digit Numbers

Mentally Adding Two-Digit Numbers

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.

  +     =     




2006-10-02 20:13:55
Viewed 2981 times Close
Math Test Online Greatmathsites

Translate

Arabic  Chinese  French  German  Italian  Japanese  Korean  Portuguese  Spanish

Feedback
Thank you to online math channels' Mathematics Department for hosting these lessons.
Copyright © 2006 - 2008 GZtrain Inc. All Rights Reserved