Mentally Adding Two-Digit Numbers

This time, it is still adding two digit numbers but we will not use paper and pencil. it will be Adding two digit numbers mentally.

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 
  • 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

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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