Speed Maths
I have posted some speed maths posts before,here are a few more tips and tricks.These are the things i forgot to mention in the other post,these few things are very simple and basic but they will help you gain some time in your quatitative sections.
1.Squares upto 25.
2.Cubes upto 12.
3.Powers of 2 upto 10.
4.Powers of 3 upto 6.
5.Multiplication tables upto 20.
6.Reciprocals of integers upto 12.
Making all these through will surely help you.All these should be in both ways like,when we see 529 in a question 23 should come to our mind automatically.Similarly when we see when we see 144,two things must come to your mind 12 x 12 and 18 x 8.
Multiplication by 11 ( just throw a look, it is very simple)
The trick is simple, start from unit place add the number in the right hand side to each digit and write it as the result in the corresponding place.To avoid confusion add a zero in the beginning and end of the number.
Eg:- Let “873421″ be the number to be multiplied with “11″.
Add zero at both ends,0-873421-0
Answer = (0+8+1)(8+7+1)(7+3)(3+4)(4+2)(2+1)(1+0)
=9607631
Hope you understood the trick.When the sum of adding the right hand digit is a two digit number put the unit place digit in the result and take tenth place digit as carry.
Multiplication by 12.
If you understood the previous multiplication then this also is simple,a small variation is there,DOUBLE each digit before adding the right digit.
Eg:- 879 x 12=?
0-879-0
Answer:=start from unit place
(9×2+0) :CARRY = 1 ANSWER=8
(7×2+9+1) :CARRY = 2 ANSWER=48
(8×2+7+2) :CARRY = 2 ANSWER=548
(0×2+8+2) :CARRY = 0 ANSWER=10548
There are tricks for multiplication by 13 also,slightly complicated yet interesting.
Here is a set of excercise problems
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