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:

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Sin = Perpendicular (P)

          Hypotenuse (H)

Cos =       Base (B)    

         Hypotenuse (H)

Tan = Perpendicular (P)

              Base (B)