Multiplication of no's near by 1000

Trick for multiplication of 981 with 991.

991*981=?

SUBTRACT

991 from 1000

u will get "09"

similarly

SUBTRACT the other

u will get "19"

now multiply "09' and "19"
we get "171"


So The last three digits are "171"

Now Just subtract

"09" from 981
or
"19" from 991

In both the above cases u will get result as "972"
This gives the first 3 digits.


Therefore,

991*981=972171


Just try it other numbers......

Properties of Square

1. A square cannot end with odd no of zeros.
2.A square cannot end with 2,3,7 or 8.
3.The square of an odd no is odd.
4. The square of an even no is even.
5. Every square is a multiple of 3 or exceeds the multiple of 3 by 1.
6.Every square no is a multiple of 4 or exceeds a multiple of 4 by 1.
7.If a square no ends in 9,the preceeding digit is even.

Square_Math

Here is a simple logic for the squares of the numbers ending with 5.

05*05=025----->0*1 5²

15*15=225------>1*2 5²

25*25=625------>2*3 5²

35*35=1225----->3*4 5²

similarly for all numbers ending with 5,simply multiply the digits before 5 with its preceding number.

For ex:-

Take 115........its square is just 11*12 followed by 25

i.e. 13225.