## Six letters

There is a word and six letters it contains.
Take one away and twelve is what remains.
What word is it?

Dozens.

There is a word and six letters it contains.
Take one away and twelve is what remains.
What word is it?

Dozens.

Can you arrange four 9's and use of at most 2 math symbols, make the total be 100?

99 / .99
or
99 + 9/9

What is the smallest number, that can be expressed as the sum of the cubes of two different sets of numbers?

Hardy-Ramanujan discovered 1729 as a magic number. Why 1729 is a magic number?
10^3 + 9^3 = 1729
and
12^3 + 1^3 = 1729
Taxicab number Ta(2)

Can you find four consecutive prime numbers that add up to 220?

47 + 53 + 59 + 61 = 220

How to measure exactly 4 gallon of water from 3 gallon and 5 gallon jars, given, you have unlimited water supply from a running tap.

Step 1. Fill 3 gallon jar with water. ( 5p – 0, 3p – 3)
Step 2. Pour all its water into 5 gallon jar. (5p – 3, 3p – 0)
Step 3. Fill 3 gallon jar again. ( 5p – 3, 3p – 3)
Step 4. Pour its water into 5 gallon jar untill it is full. Now you will have exactly 1 gallon water remaining in 3 gallon jar. (5p – 5, 3p – 1)
Step 5. Empty 5 gallon jar, pour 1 gallon water from 3 gallon jar into it. Now 5 gallon jar has exactly 1 gallon of water. (5p – 1, 3p – 0)
Step 6. Fill 3 gallon jar again and pour all its water into 5 gallon jar, thus 5 gallon jar will have exactly 4 gallon of water. (5p – 4, 3p – 0)

The digits 0-9(0,1,2,3,4,5,6,7,8,9) can be rearranged into 3628800 distinct 10 digits numbers.
How many of these numbers are prime?

None. The sum of numbers from 0-9(0,1,2,3,4,5,6,7,8,9) is 45 and therefore can be divisible by 3 and 9.

What is the value of 1/2 of 2/3 of 3/4 of 4/5 of 5/6 of 6/7 of 7/8 of 8/9 of 9/10 of 1000?

100. Looks hard? Don't worry, just work it backwards and you'll find it very easy.

We all know that square root of number 121 is 11. But do you know what si the square root of the number "12345678987654321" ?

111111111
Explanation:
It's a maths magical square root series as :
Square root of number 121 is 11
Square root of number 12321 is 111
Square root of number 1234321 is 1111
Square root of number 123454321 is 11111
Square root of number 12345654321 is 111111
Square root of number 1234567654321 is 1111111
Square root of number 123456787654321 is 11111111
Square root of number 12345678987654321 is 111111111 (answer)

Think of a number. Double it. Add ten. Half it. Take away the number you started with. What is your number?

Your number is 5.

What is the largest number you can write with just 3 digits?

999.