irfad

irfad
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Member since: Aug 10 2009, 12:19 AM EDT
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Hello, my name is irfad!
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BIO

Insert your profile picture here!Occupation:none
Home town:islamabad
Location:pakistan
Astrological sign:ia

irfad the king
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MORE ABOUT ME...

The best word to describe me is:moon

Interests:playing game :D

My hero(es):sharukh

My superpower is:mom

If I could live anywhere, it would be:amazing

My dream job(s):doctor

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irfad Multiply By 4 0 Aug 10 2009, 1:11 AM EDT by irfad
Thread started: Aug 10 2009, 1:11 AM EDT  Watch
Multiply By 4

To quickly multiply by four, double the number and then double it again.
Often this can be done in your head.
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irfad Square 2 Digit Number: UP-DOWN Method 0 Aug 10 2009, 1:08 AM EDT by irfad
Thread started: Aug 10 2009, 1:08 AM EDT  Watch
Square 2 Digit Number: UP-DOWN Method
Square a 2 Digit Number, for this example 37:
Look for the nearest 10 boundary
In this case up 3 from 37 to 40.
Since you went UP 3 to 40 go DOWN 3 from 37 to 34.
Now mentally multiply 34x40
The way I do it is 34x10=340;
Double it mentally to 680
Double it again mentally to 1360
This 1360 is the FIRST interim answer.
37 is "3" away from the 10 boundary 40.
Square this "3" distance from 10 boundary.
3x3=9 which is the SECOND interim answer.
Add the two interim answers to get the final answer.
Answer: 1360 + 9 = 1369

With practice this can easily be done in your head.
Thanks To Ryan
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irfad Square a 2 Digit Number Ending in 5 0 Aug 10 2009, 1:07 AM EDT by irfad
Thread started: Aug 10 2009, 1:07 AM EDT  Watch
Square a 2 Digit Number Ending in 5

For this example we will use 25
Take the "tens" part of the number (the 2 and add 1)=3
Multiply the original "tens" part of the number by the new number (2x3)
Take the result (2x3=6) and put 25 behind it. Result the answer 625.
Try a few more 75 squared ... = 7x8=56 ... put 25 behind it is 5625.
55 squared = 5x6=30 ... put 25 behind it ... is 3025. Another easy one! Practice it on paper first!

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irfad Finger Math: 9X Rule 0 Aug 10 2009, 1:06 AM EDT by irfad
Thread started: Aug 10 2009, 1:06 AM EDT  Watch
Finger Math: 9X Rule

To multiply by 9,try this:
(1) Spread your two hands out and place them on a desk or table in front of you.
(2) To multiply by 3, fold down the 3rd finger from the left. To multiply by 4, it would be the 4th finger and so on.
(3) the answer is 27 ... READ it from the two fingers on the left of the folded down finger and the 7 fingers on the right of it.

This works for anything up to 9x10!
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irfad maths 1 Aug 10 2009, 1:05 AM EDT by Rune-Master5
Thread started: Aug 10 2009, 1:04 AM EDT  Watch
The 11 Rule
You likely all know the 10 rule (to multiply by 10, just add a 0 behind the number) but do you know the 11 rule? It is as easy! You should be able to do this one in you head for any two digit number. Practice it on paper first!
To multiply any two digit number by 11:

For this example we will use 54.
Separate the two digits in you mind (5__4).
Notice the hole between them!
Add the 5 and the 4 together (5+4=9)
Put the resulting 9 in the hole 594. That's it! 11 x 54=594
The only thing tricky to remember is that if the result of the addition is greater than 9, you only put the "ones" digit in the hole and carry the "tens" digit from the addition. For example 11 x 57 ... 5__7 ... 5+7=12 ... put the 2 in the hole and add the 1 from the 12 to the 5 in to get 6 for a result of 627 ... 11 x 57 = 627
Practice it on paper first!

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