Archive for the ‘Mental Maths’ Category
Wednesday, October 31st, 2007
There are many ways to solve and simplify a math problem. A simple math division can also be done differently mentally. It boils down to which is the suitable approach at that time. It also depends on one's preference in solving the math question.
To review mental division using numerator approach, ...
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Wednesday, October 31st, 2007
How is mental division done?
Let's us do an example to illustrate:
40 / 7
Mental solution:
Step 1:
Break up as much as possible the original dividend 40 in term of 7 ==> (7 X 5) + 5
Step 2:
Divide the answer in step 1 by original divisor 7 ==> (7 x 5 )/7 + 5/7 = ...
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Tuesday, October 30th, 2007
Mentally multiplying one digit by one digit is simple (normally memorise answer).
Mentally multiplying 2 digits by one digit? Maybe OK.
Principle of 2 digit by one digit mental multipication:
Expand the 2 digit to include a 10's number.
Example: 45 ==> 40 + 5
Let's do an example: 45 x 6
Mental solution: (40 + ...
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Tuesday, October 30th, 2007
Of the 3 approaches in mental number squaring, this approach is more conceptual.
See an overview of the 3 approaches here.
Principle: (a - b) (a + b) = a2 - b2
But note that "b" is the difference to make the original number go to a 10's.
Example: 34 ==> a = 34 ...
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Tuesday, October 30th, 2007
In this (a - b)2 approach to mental number squaring, the concept is to split the original number to one having 10's. It is similar to the ( a + b)2 approach but differs in the expanded expression.
Principle: (a - b)2 = a2 - 2ab + b2
Example: 342
Step 1: Split 34 ...
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Tuesday, October 30th, 2007
In this (a + b)2 approach to mental number squaring, the trick is to split the original number to one having 10's. Then apply the (a + b)2 expansion to solve the multiplication. Dealing with 10's is simpler than dealing with non-10's.
Principle: (a + b)2 = a2 + 2ab + ...
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