Can someone help me understand whether the actual method used manually is wrong please and how?
42 x
48
Ans 1:
Workings
0336+
1680 =
2016
It would be nice to have custom front-end controls for Latex and other advanced math on this forum, it would make my life easier when I have mathematical problems to discuss and verify usually they are more complicated than this.
A teacher figured out that 42 x 48 can be estimated as follows but the accuracy is not very consistent as I have encountered incorrect calculations, is the teacher incorrect or the method missing some refined calculation I am not aware of?
42 x 48 = 2016 [LibreOffice Calc / Microsoft Calculator shipped with Windows Server 2007]
The workings basically read:
40 x 80 = 3200
2 x 8 = 16
3200 + 16 = 3216
Still the answer is wrong, does anyone know these methods of estimation and how they can be improved?
A theoretic paper and books on mathematical can be included in the reply I don't mind reading, I am a teacher
However I like to double check every little problem.