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Shyam Lal Naik (Service) (6156 Points)

24 July 2010

when the numbers 1,2 .. n are written in words, the alphabet "a" appears for the first time in 1000.

"a" does not appear from "one" to "nine hundred ninty nine".

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7 Replies

Akhil Gupta (Manager F&A) (856 Points)
Replied 24 July 2010

1 * 8 + 1 = 9

1 2 * 8 + 2 = 9 8

1 2 3 * 8 + 3 = 9 8 7

1 2 3 4 * 8 + 4 = 9 8 7 6

1 2 3 4 5 * 8 + 5 = 9 8 7 6 5

1 2 3 4 5 6 * 8 + 6 = 9 8 7 6 5 4

1 2 3 4 5 6 7 * 8 + 7 = 9 8 7 6 5 4 3

1 2 3 4 5 6 7 8 * 8 + 8 = 9 8 7 6 5 4 3 2

1 2 3 4 5 6 7 8 9 * 8 + 9 = 9 8 7 6 5 4 3 2 1

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Akhil Gupta (Manager F&A) (856 Points)
Replied 24 July 2010

1 * 1 = 11

11 * 11 = 121

111 * 111 = 12321

1111 * 1111 = 1234321

11111 * 11111 = 123454321

111111 * 111111 = 12345654321

1111111 * 1111111 = 1234567654321

11111111 * 11111111 = 123456787654321

111111111 * 111111111 = 12345678987654321

1 Like

Akhil Gupta (Manager F&A) (856 Points)
Replied 26 July 2010

MATH TRICKS #1

STEP 1
Ask a friend to write down a number (any number with more than 3 digits will do, but to save time and effort you might suggest a maximum of 8 digits).
Example: 83 972 105

STEP 2
Ask them to add the digits.
Example: 8+3+9+7+2+1+0+5 = 35

STEP 3
Ask them to subtract this number from the original one.
Example: 83 972 105 – 35 = 83 972 070

STEP 4
Ask them to select any digit from this new number and strike it out, without showing you.
Example: 83 972 070

STEP 5
Ask them to add the remaining digits and write down the answer they get.
Example: 8+3+9+7+0+7+0 = 34

STEP 6
Ask them to tell you the number they get (34) and you will tell them which number they struck out.

SOLUTION
The way you do this is to subtract the number they give you from the next multiple of 9. The answer you get is the number they struck out.
Example: The next multiple of 9 here is 36 (9 x 4 =36)
36 – 34 = 2 and there you have your answer, easy isn’t it!

Note: If the number they give you after step 5 is a multiple of 9, there are two possible answers then you simply tell them that this time they crossed out either a 9 or a zero.

Akhil Gupta (Manager F&A) (856 Points)
Replied 26 July 2010

MATH TRICKS #2

Amazing 1089...

Step 1
Take two pieces of paper and hand one to a friend.
On yours, without letting them see, write the number 1089, then fold the paper to keep it hidden.

Step 2
Ask them to think of a 3-digit number but, before they write it down, ask them to put the numbers in order from greatest to smallest. Don't let them show what they've written.
Example: 543

Step 3
Below their number, ask them to write the same digits, but in reverse order, from smallest to greatest.
Example: 345

Step 4
Now, ask them to subtract the new lower number from the original one they wrote.
Example: 198

Step 5
Next, ask them to reverse the order of that number.
Example: 891

Step 6
Then, get them to add this latest number and the previous number together and show you the result.
Example: 891 + 198 = 1089

Step 7
Finally, you can reveal your own number, which (if they have calculated correctly) will be exactly what they have written...
1089

Amazing!

Akhil Gupta (Manager F&A) (856 Points)
Replied 26 July 2010

MATH TRICKS #3

Try this one in your head, using mental maths...

Step 1
Ask a friend to think of a number between 1 and 10.
Example: 8

Step 2
Get them to double it.
Example: 16

Step 3
Ask them to add 10 to the answer.
Example: 26

Step 4
Then get them to divide by 2.
Example: 13

Step 5
Ask them to tell you what number they now have.
Example: 13

Step 6
You subtract 5 from this and tell them what their original number was.
Example: 13 - 5 = 8

Note: If you wish to take turns to practice your mental maths, you can also use 2 and 3 digit numbers to make it harder!

Akhil Gupta (Manager F&A) (856 Points)
Replied 26 July 2010

Magic Squares

A magic square is a set of integers arranged in a square in such away that each row, each column (and often the two diagonals as well) sum to the same number.
For example: This 3 x 3 magic square's rows, columns and diagonals each add up to the number 15.

4	9	2
3	5	7
8	1	6

This 4 x 4 magic square's rows, columns and diagonals each add up to the number 34.

3	6	10	15
13	12	8	1
16	9	5	4
2	7	11	14

Akhil Gupta (Manager F&A) (856 Points)
Replied 26 July 2010

Squares

The result of squaring a number can also be arrived at by progressively adding consecutive odd numbers as shown below.

1²	= 1	= 1
2²	= 4	= 1+3
3²	= 9	= 1+3+5
4²	= 16	= 1+3+5+7
5²	= 25	= 1+3+5+7+9
6²	= 36	= 1+3+5+7+9+11
7²	= 49	= 1+3+5+7+9+11+13
8²	= 64	= 1+3+5+7+9+11+13+15
9²	= 81	= 1+3+5+7+9+11+13+15+17
10²	= 100	= 1+3+5+7+9+11+13+15+17+19