The sum of 9 + 2 would be 11 and the sum of 50 + 30 would be 80. The total sum is 91.
- If you try to estimate, you first sum 50 + 30 and so you can estimate that the number will be somewhere close to 80.
- Now you can add the 9 form 39 to this number, and you can get even a more precise estimative saying the number will be approximately 89.
- Finally you add two to that number and you get the final correct answer.
Hope it helped,
BioTeacher101
