Thursday

July 24, 2014

July 24, 2014

Posted by **Kelly** on Wednesday, August 30, 2006 at 6:08pm.

For how many two-digit numbers if the ones digit larger than the tens-digit? Can you find a systematic way to arrive at the number?

Ok, every 2-digit number looks like xy, where x is the 10's digit and y is the one's digit. It should be apparent that x runs from 1 to 9.

If x is 1 then y runs from 2 to 9, or 8 digits

If x is 2 then y runs from 3 to 9, or 7 digits

.

.

.

If x is 8 then y = 9, or 1 digit.

For x=9, 0 digits.

If we count up the numbers possible for y we add the integers 1+2+3+4+5+6+7+8

Put that into google if you want or just add it up.

The numbers you seek look like the following, the one's digit being preceded by each of the integers to the left of the right hand number

12

123

1234

12345

...

...

...

123456789

So you have

2 + 3 + 4+ 5 + 6 + 7 + 8 + 9 = ?

The sum of the first n integers starting with 1 is S == n(n += 1)/2

Therefore, the sum of your numbers is S = n(n + 1) - 1

Please HElPPP!!!!!!!!!!

Is it possible to arrange numbers 1 through 16 in a 4 by 4 grid so that consecutive numbers are not touching? If so, how did you do it and also can you find more than one solution?

Please Help I don't understand THIS !!!!!!!!!!!

THANKS!!!!!!!!

Does this work?

1,

**Related Questions**

math - i am a 4 digit number.my thousands didgit is 4 less than my tens digit.my...

math - my thousand digit is half my ones digit.my houndreds digit is odd and ...

maths I need answer - A 2-digit number has a greater tens digit than the ones ...

4th grade - i am a 5 digit number my tens digit is the sum of my hundreds digit ...

Math - The mystery number's tens digit is less than the ones digit. The tens ...

Math - i am a 4 digit number between 3000 and 4000.My ones digit is twice my ...

math - My thousands digit is twice my hundreds digit. The sum of my tens and ...

5th grade math - i am a number greater than 40,000 and less than 60,000 my ones ...

math - i have a six digit question my 100 thousands is one less than my ones ...

math - i am a 3 digit number when i am rounded to the nearest hundred i become ...