Monday, May 2, 2016



Don’t look up this word in Dictionary.

Alphametics is the combination of two words – Alphabetic + Arithmetic when combined in a form of mathematical puzzle a new word was born in 1955 known as Alphametics.

In simple word it is a mathematical puzzle consisting of a numerical computation with letters substituted for numbers which are to be restored through mathematical reasoning.

What is odd and even?

As far as the definition of odd and even in mathematics is concerned a number that ends with 1, 3, 5, 7 and 9 is known as odd number whereas a number that ends with 0, 2, 4, 6 and 8 is known as even number.

Now a big question is – Have you heard about Odd and Even scheme brought by Mr. Arvind Kejriwal Govt. to reduce the pollution level of Delhi?

If you live in Delhi then you must have heard about it. The pollution level of Delhi is in very critical stage and in a recent report it was found that the air in Delhi is most polluted and the govt. of Delhi has brought a scheme to reduce the pollution level by allowing the cars with even number to ply on Even dates and odd registration number car to ply on odd dates.

This puzzle is a salute to the govt. of Delhi for their bold decision taken to reduce the pollution level and make Delhi road congestion free.

Here E = Even number and O = Odd number
Replace E with even digits and O with odd digits. The digit may change. Find a solution?

Let us first represent this question by replacing every O and E with another alphebets

As you can see that in the fourth row –

A B C × D = K L M which is a three digit number. If you take E = 2 and A = 3 then 322 × 3 = 966 looks true for the 4th row but it fails to satisfy the 3rd row because in third row A B C × E = F G H I which is a four digit number.

If A = 1 then obviously A B C < 200 then whatever value you assign for B and C you will get a four digit number < 2000 but it contradicts the facts as F = even number. Hence A = 3 and 3 × D = K where K < = 9 because K is an even number. Therefore D = 2 as 3 × 4 = 12 is a two digit number. A = 3 D = 2 Let’s check the given expression with these two values.

It is clear from the above equation that A B C × E > 2100 then E will take the value of 6 and 8.

It doesn’t satisfy the 5th row which is a 5 digit number. Hence we have to take another value of B, C and D to satisfy the expression.
Let’s take B = 4 and C = 8 = D


Tuesday, March 15, 2016

Phone number tells your age


If I tell you that I can predict your age and that too with your mobile /phone number; you won’t believe my words. But this is absolutely true. Are you ready to play the game?

If yes, take your pen and paper out and get ready to enjoy the beauty of numbers.

• Tell your friend to write the last four digits of his mobile/phone number.

• Reverse the number

• Subtract the smaller one from the larger one.

• Ask him to add together the digits of the resulting number until he gets a single digit number.
Example :- 1456 = 1 + 4 + 5 + 6 = 16 and 16 = 1 + 6 = 7

• Finally ask him to subtract the single digit number from the last two digits of his birth year.

• Now enquire the last result from your friend.

Once you get the final result of your friend add 9 to it to get the age of your friend.

Example: - Your friend’s mobile number = 9838420804

Last four digits = 0804

Reverse the digit = 4080

Subtract the smaller from the larger one = 4080 – 0804 = 3276

Add the digits = 3 + 2 + 7 + 6 = 18 and 18 = 1 + 8 = 9

If your friend was born in 1974; the last two digits of your birth year = 74

Subtract the single sum digit from the last two digits of your birth year = 74 – 9 = 65

The final result = 65

Once your friend tells you the final result simple add 9 to it = 65 + 9 = 74

Hence you birth year = 1974

Your present age = 2016 – 1974 = 42 years

Read my blogs on number at

Dr Rajesh Kumar Thakur

Cycle of Four

Cycle of Four

In this puzzle you will get the taste of real FOUR. This is one of my all-time favorite game and I do hope you will also love to play it. The best part of this game is that you don’t need any calculator to do this game.
Are you ready for this game?

1. Think of a number from 1 to 100

2. Write down its name using English alphabets

3. Count the number of letters in its name to obtain the second number.

4. Count the number of letters in the second number to obtain the third number.

5. Repeat the pattern until you get the same number repeating


I have got your final result. Your last number will be FOUR. You would be surprised to know that any number you take the last repeated number will be FOUR.


Suppose Your number = 73

73 in English alphabet = SEVENTY THREE

Count the number of letters = 12

Second Number = TWELVE

Number of letters = 6

Third Number = SIX

Number of letters = 3

Fourth Number = THREE

Number of letters = 5

Fifth number = FIVE

Number of letters = 4

Sixth Number = FOUR

Number of letters = 4

Seventh Number = FOUR

Repetition starts now so stop here and you can see that after every successive attempt you will get FOUR

Read my blogs on Number at

Dr Rajesh Kumar Thakur

Monday, March 14, 2016

Know Your Mobile Number

This puzzle can help you to know the mobile number of any of your friends who pretend to divulge his mobile number. I have made this puzzle in 2007. Let's enjoy the game.

1. Multiply your Mobile number by 80

2. Add 1 to it

3. Multiply the previous sum by 250

4. Add 1750 to it

5. Divide the last result by 2000

Hey, are you ready with your answer?

No, not yet. Take your time.

Ok, finally you have come up with your answer. I will now do some magical work to know your mobile number. You are like my friend, so I am revealing my magical art to you but you have to give me a promise that when you play this game with you friends, you won't reveal it to him. I shall do these operations.

6. Subtract 1 from your final result.

7. Divide your result by 10

Let me count the digits. It is 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. Oh, it is a 10 digit number. Isn't it your mobile number.

Example :- My mobile number = 9868060804

Multiply it by 80 = 9868060804 x 80 = 989444864320

Add 1 to it = 989444864320 + 1 = 989444864321

Multiply it by 250 = 989444864321 x 250 = 197361216080250

Add 1750 = 197361216080250 + 1750 = 1973612160802000

Divide it by 2000 = 1973612160802000 / 2000 = 98680608041

It is my turn to tell you your mobile number.

Subtract 1 from the last result = 98680608041 - 1 = 98680608040

Divide it by 10 = 9868060804

Mobile Number = 9868060804

Rate this lovely game by mailing me your views

Dr. Rajesh Kumar Thakur

Thursday, January 21, 2016

Find Number of Brother, sister and friends

Tell Brothers, Sisters and Friend of anyone

This puzzle will let you know the number of brothers, sisters and close friends your friend do have through a recreational mathematical puzzle. Are you ready to play this game with your friends? This game is based on mathematical calculation so please don’t use calculator or any electronic device as it will ruin the purpose of the game. Mathematical games are the best exercise for your brain so keep doing the calculation in your head or do manual calculation.

Before I come to the game let me advise you to be alert while playing this game with your near and dear ones. Take a piece of paper and pen and give it to your friend or someone with whom you want to play this game. I am sure at the end of this game you are definitely going to get a good response from the audience.

Here comes the steps which you will dictate and your friend will follow.

• Ask your friend to write the number of his/ her sister on a piece of paper and multiply it by 2.
• Add 3 to that total.
• Now multiply the result by 5 and add the number of brothers to this number.
• Further multiply this number by 10 and add the number of your close friends to it.
• I think you are OK with the calculation. In order to tell you the correct answer I will finally ask you to add 125 to the result and tell me the final answer.
• I have to blow the whistle this time by giving you the correct answer. Wait let me subtract 275 from your final result and come to the answer.
• You will have a 3 digit number at the end of the game. The number at the hundred place tells you the number of sisters and the number places at ten’s digit is the number of brother and the unit digit tells you the number of good friends you have.

Isn’t it a funny and mind blowing game?

Example: - Suppose you have 3 sisters, 2 brothers and 4 close friends. Let’s begin the calculation to check how effective this game is.
• Number of sister × 2 = 3 × 2 = 6
• Add 3 to it = 6 + 3 = 9
• Multiply it by 5 = 9 × 5 = 45
• Add number of brothers to it = 45 + 2 = 47
• Multiply the result by 10 = 47 × 10 = 470
• Add number of close friends to it = 470 + 4 = 474
• Add 125 to it and tell me the result = 474 + 125 = 599
• Finally I shall subtract 275 from your result = 599 – 275 = 324

Now the question is – Why this puzzle works?

A three digits number with its digits X, Y and Z = 100X + 10Y + Z
• Multiply Number of sister (X) by 2 = X × 2 = 2X
• Add 3 to it = 2X + 3 = 2X + 3
• Multiply it by 5 = (2X + 3)× 5 = 10X + 15
• Add number of brothers (Y) to it = 10X + 15 + Y
• Multiply the result by 10 = (10X + 15 + Y)× 10 = 100X + 10Y + 150
• Add number of close friends (Z) to it = 100X + 10Y + 150+ Z
• Add 125 to it and tell me the result = 100X + 10Y + 150+Z + 125
• Finally I shall subtract 275 from your result = 100X + 10Y + Z+ 275 – 275 = 100X + 10Y + Z

The three digit number with X at hundred place, Y at the Ten’s place and Z at the unit place = 100X + 10Y + Z

Dr Rajesh Kumar Thakur

Number of Fans and Tubelight

Count the number of fan and tube light

This is a unique puzzle that will help you to play a very funny mathematical game with your friends that will let you guess the number of fan and tube light at his home without being there. Every household has fan, tube –light and many other electronics appliances. This game will let you know about two of the appliances present at your friends’ house whether it be tube-light, fan, LCD or any other appliances. For the convenience of reader this game has been based here on fan and tube light.

Tell your friend to do the following calculation on his copy as instructed by you.

1. Multiply the number of fan at your home by 2

2. Add 4 to it

3. Multiply it by 5

4. Add the number of tube-light at home to the previous result.

5. Subtract 20 and tell the final result

The result which your friend will give you have two digits. The number at the ten’s place will be the number of fan at his house and the digit at the unit place will tell you the tube light at home.

Example:- Suppose there are 5 fans and 8 tube-lights in your friend’s house. Let’s see the calculation as instructed.

1. Multiply the number of fan at your home by 2 = 5 × 2 = 10

2. Add 4 to it = 10 + 4 = 14

3. Multiply it by 5 = 14 × 5 = 70

4. Add the number of tube-light at home to the previous result = 70 + 8 = 78

5. Subtract 20 and tell the final result = 78 -20 = 58

Once your friend tells you his final result you can instantly tell the number of fans and tube- light present in his home.
5 8
Number of fan Number of tube- light

How does this puzzle work?

We know that a two digit number with x at ten’s place and y at the unit place = 10x + y

If x represent the number of fan at home and y represents the number of tube- lights at home then you will get the final result = 10x + y.

Let’s see the trick behind this puzzle.

1. Multiply the number of fan at your home by 2 = 2x

2. Add 4 to it = 2x + 4

3. Multiply it by 5 = (2x + 4) × 5 = 10x + 20

4. Add the number of tube-light at home to the previous result = 10x + 20 + y

5. Subtract 20 and tell the final result = 10x + 20 + y – 20 = 10x + y

Rajesh Kumar Thakur