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Friday, 23 March 2012

IBPS MATHEMATICS | SSC MATHEMATICS | CHAPTER 3 NUMBER SYSTEM

Here I will show you how to find least and greatest element in a series.

Basically there are 2 methods for determing this.

Lets take an example first.
Question: which one of the following fraction is the greatest?
                3/4, 4/5 and 5/6
Solution:
                First method: calculate its decimal equivalent and find greatest.
                                3/4=0.75 ; 4/5= 0.8 ; 5/6= 0.833
                So greatest is 5/6
                Second method:
                Find the LCM of denominator and change denominator of all by LCM so obtained.
                The number with largest numinator is greatest fraction.

Shortcut method and which can be done mentally.
First study this relationship:

Now we see that increase in numinator is 1 and increase in denominator is 1
And 1> 3/4 so, last value is greatest.
similarly, we can solve
Question: which one of the following fraction is the greatest?
2/7, 4/15 and 6/23.

This was first method second method Tomorrow.
Please add your comment for encoragement.

Friday, 16 March 2012

IBPS MATHEMATICS | SSC MATHEMATICS | CHAPTER 2 MULTIPLICATION

SHORTCUT METHOD FOR MULTIPLICATION:

Multiplication by 11

The last digit of the multiplicand (the number multiplied) is put down as the right hand figure of the answer.
Each successive digit of the multiplicand is added to its neighbor at the right.

Example:

5892 X 11 =?
Change it to 05892 x 11=?

Step 1: put down last digit of 05892
                                05892 x 11=_ _ _ _ 2
Step 2: Each successive digit of 05892 is added to its neighbor at the right. That is

               9+2=11, write 1 and carry over 1 to next.
                05892 x 11=_ _ _ 1 2        carry 1

                8+9= 17 + carry = 17 +1 = 18. Write 8 and carry over 1.
                05892 x 11=_ _ 8 1 2        carry 1

                5+8= 13 + carry = 13 +1 = 14. Write 4 and carry over 1.
                05892 x 11=_ 4 8 1 2         carry 1.

                0+5= 5 + carry = 5 +1 = 6. Write 6
                05892 x 11=6 4 8 1 2         carry 0.

Multiplication by 12

Double the last digit of multiplicand and write as the right hand figure of the answer
Double Each successive digit of the multiplicand is added to its neighbor at the right.

Example:

5892 X 12 =?
Change it to 05892 x 12=?

Step 1: put down double of last digit of 05892
                                05892 x 11=_ _ _ _ 4
Step 2: double Each successive digit of 05892 is added to its neighbor at the right. That is
               9*2+2=20, write 0
               05892 x 12=_ _ _ 0 4        carry 2

               8*2+9+ carry = 25 + carry = 25 +2 = 27. Write 7 and carry over 2.
               05892 x 12=_ _ 7 0 4        carry 2

                5*2+8 + carry= 18 + carry = 18 +2 = 20. Write 0 and carry over 2.
                05892 x 12=_ 0 7 0 4         carry 2

                0*2+5 + carry= 5 + carry = 5 +2 = 7. Write 7
                05892 x 12=7 0 7 0 4         carry 0

Answere is 70704