Today's question

Find a three-digit number such that the number is divisible by each digit of the number and all the digits are prime. You can post your answers as comment.

Multiplying two-digit numbers by 11

To multiply a two digit number by 11, write the ones digit of the two-digit number at the ones place of the answer.

Add the ones and tens digit to get the middle number of the answer.

Write the tens digit of the number at the hundreds place of the answer.

Example:

To multiply 43 by 11, write 3 at the ones place of the answer.

Add the ones and tens digit (4 + 3 = 7), 7 is the middle number of the answer.

The tens digit 4 is in the hundreds place of the answer.

Thus, 43 x 11 = 473

Answer to previous question

The pairs are

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

Today's question

Make the numbers from 1 to 16 as 8 pairs of numbers. The sum of each pair should be a perfect square. You can post your answers as comments.

Easy division by 9

A repeated pattern is produced when a number smaller than 9 is divided by 9.

Example:

1. 7/9 = 0.777... (This will work if the dividend is from 1 to 8 and the divisor is 9)

2. 86/9 = 0.8686... (This will work if the dividend is from 10 to 98 and the divisor is 99)

3. 5/99 = 0.0505... (This will work for dividends 1 to 9 and divisor 99)

4. 594/99 = 0.594594... (This will work for dividends 100 to 998 and divisor 999)

5. 74/999 = 0.074074... (This will work for dividends 10 to 99 and divisor 999)

6. 3/999 = 0.003003... (This will work for dividends 1 to 9 and divisor 999)

Answer to previous question

All cubes are in the form 7n + 1. That is, when 1 is added or subtracted from the cube, they will be multiples of 7.

                  

                  2x2x2 = 8 = (7x1) + 1

                  3x3x3 = 27=(7x4) - 1

                  4x4x4 = 64=(7x9) + 1

                  5x5x5 = 125=(7x18) + 1

Today's Question

The cube of any integer is in relation with 7. Can you find the relation?

Numerical Palindrome

A palindromic number is a number which reads the same forward and backward. 

• Write any whole number.
• Reverse its digits and add to the previous number.
• To this sum add the number formed by reversing the sum’s digits.
• Continue this process. Ultimately you will reach a palindromic number.

Example:

• Let’s start with 3659.
• Reversed number is 9563.
• Sum of the two numbers is 3659 + 9563 = 13,222.
• Continuing the process we get 13,222 + 22,231 = 33,453 (palindromic number).

Answer to previous question

Using eight 8s 1000 can be expressed as
888 + 88 + 8 + 8 + 8 = 1000
Congratulations to all those who got it right.

Today's question

Using eight 8s, try to get the value of 1000. Post your answers as comment.

Calculation race

Ask your friend to write any two-digit number and multiply it manually by 3367.

You will always be able to get the answer before him/her without a calculator.

Example: If your friend chooses 53, then write 535353 and divide it by 3.

Thus, 535353/3 = 178451

Check: 53 x 3367 = 178451

Trick: Write the two-digit number thrice and divide it by 3.

Answer to previous question

The possible solutions to the question are:

98765 + 1234 = 99999

97864 + 2135 = 99999

96125 + 3874 = 99999

Today's question

 Make two numbers using each digit from 1 to 9 only once. The sum of the numbers must be 99999. Can you do it? There can be more than one possibility. Post your answers as comment.

Easy multiplication by 9

To multiply a number by 9, multiply it by 10 and then subtract the original number.

Example: To multiply 139 by 9, first multiply 139 by 10.

139 x 10 = 1390

Next subtract 139 from 1390.

1390 – 139 = 1251

Thus 139 x 9 = 1251

Answer to previous question

The answer to previous question is 4913. 4 + 9 + 1 + 3 = 17.

17 x 17 x 17 = 4913.

Today's question

I suppose a four-digit number. The cube of the sum of the digits is equal to the number itself. Can you say which is the number?

Answer to Wednesday's question

The number which gives the same result when multiplied by 5/4 and when added to 5/4 is 5.

Multiplying big numbers by 11

To multiply big numbers by 11, first multiply the number by 10 and then add the original number to the product.

Example: To multiply 9876 by 11 first multiply it by 10 (9876 x 10 = 98760)
Add 9876 to 98760 (9876 + 98760 = 108636)

Mysterious 24

If you square any prime larger than 3 and subtract 1, the answer will always be divisible by 24.

Example:  19 x 19 = 361, 361 – 1 = 360

360/24 = 15

Today's question

Today’s question:

Which number when multiplied by 5/4 gives the same result as when added to 5/4?

Post your answers as comment. The answer will be published on Friday.

Magic number

Factors of 1,274,953,680

The number 1,274,953,680 has all the digits from 0 to 9. It is divisible by all the numbers from 1 to 16.

Answer to yesterday's question

The answer to yesterday’s question:

The next number in the sequence 4,6,8,9 is 10. They are the composite numbers in order.

Today's question

Today’s question:

Which is the next number of the sequence 4,6,8,9,……..?

7-11-13 trick

Ask a friend to write any three digit number on a sheet of paper.

Ask him/her to multiply the number by 7, then by 11 and finally by 13. (You can give him/her a calculator)

You will still get the answer quicker than your friend.

Trick: Just write the three digit number twice to get the answer.

Example: Let 452 be the number chosen by your friend. 452 x 7 x 11 x 13 = 452452. That is the same as 452 written two times.

Mnemonic

A mnemonic is a word, rhyme or any sentence which helps us to remember some rule, formula etc.

The following mnemonic helps us in remembering the trigonometric ratios:

Some People Have Curly Brown Hair Turned Permanently Black

Sin = Perpendicular (P)

          Hypotenuse (H)

Cos =       Base (B)    

         Hypotenuse (H)

Tan = Perpendicular (P)

              Base (B)

Answer to yesterday's question

The answer to yesterday’s question:

The smallest number exactly divisible by numbers from 1 to 10 is the numbers’ LCM which is 2520.

Today's question

Today’s question:

Which is the smallest number exactly divisible by numbers from 1 to 10?

You can attempt to answer this through your comments. The answer will be published tomorrow in our blog.

Easy multiplication

Easy method to multiply by 5:

In order to multiply a number by 5, add a 0 to right of the number or multiply by 10 and then, divide it by 2.

For example, suppose 426 is to be multiplied by 5. When a zero is added to it or it is multiplied by 10, it becomes 4260. When it is divided by 2, we get 2130. That is, 426 x 5 = 2130.

First Post

Greetings everyone! We are launching our blog here by posting the oldest number puzzle in mathematics. This was once shown in an English movie. The riddle goes like this:

As I was going to St. Ives,

I met a man with seven wives,

Every wife had seven sacks,

Every sack had seven cats,

Every cat had seven kits,

Kits, cats, sacks and wives,

How many were going to St. Ives.

This seems like a very complicated puzzle. But the answer lies in the question itself. Only one person that is, the speaker was going to St. Ives. He met the remaining people on his way. All mathematical problems are similar to this. Read the question more than once before locking an answer. It is easy to underestimate a problem and lead to a wrong conclusion. So always think twice before you act.

Our Launch

"Education is the manifestation of the perfection already in man", so said Swami Vivekananda. Herewith, we are starting a journey into the wonderful of mathematics to provide oppurtunities to all so that they may rise to their fullest potential. The world is full of oppurtunities and experiences. Every experience is an oppurtunity to learn something new. We should strive to allow the light of knowledge to create a difference in our lives. He who can rise up to a challenge and make a difference is the one with an unwavering belief in himself.  Through this blog our objective is to help each and every one of you in all possible ways, to move forward in this context. All of you are free to post any of your doubts or queries regarding mathematics and if possible they will be answered within a period of time(minimum 24 hours). We will also be including puzzles, quizzes and other interesting facts. This blog is created and run by a post graduate who has always been passionate about this subject. She will be online from 7 to 8 pm. We will start functioning from the 27th of May, 2013. Hope that the help we offer will make a difference in your search and we look forward to your support and encouragement.