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How many one-digit numbers are twice the size the sum of their digits?
None. The sum of one digit can't be twice the size of the digit.
How many 8 digit numbers are there with 3 different digits where the smallest of the 3 occur twice and the other thrice?
Excluding numbers which begin with 0, there are 67,200 of them.
How many two-digit numbers are twice the sum of their digits?
Only one . . . . . 18
How many 3 digit whole numbers can you write using the digits 1 3 5 and 7 if no digit can be used twice?
24.
How many 5-digit numbers can be made only using the numbers 1 2 3 4 5 with out repeating a number twice example 12345 12354 12435?
120 5-digit numbers can be made with the numbers 12345.
How many 4 digit numbers can you form from the digits 1 2 3 4 5 where no digit is used twice?
5*4*3*2 = 120
How many different four digit combinations are there of the numbers zero through nine and using one number twice in the combination?
There are 360 of them.
How many 7 digit telephone numbers can be formed the first digit cannot be zero?
9,000,000 if there are no other requirements.
How many different numbers between 250 and 400 have '2' as the tens digit?
That would be the numbers in the form "32x" (where "x" can be any digit). In other words, ten numbers.
How many four digit numbers can you foum from the digits 1 2 3 and 5 where no digit is used twice?
As no digit is used twice then you have 4 choices for the first digit, but only 3 choices for the 2nd digit, 2 for the 3rd and just one for the 4th. 4 x 3 x 2 x 1 = 24 combinations.
How many 2-digit numbers are there in which the one digit in greater than tens digit?
Oh, what a lovely question! If we're looking for 2-digit numbers where the one's digit is greater than the ten's digit, we simply need to think about the possibilities. There are 36 such numbers, ranging from 12 to 98. Just imagine all the happy little numbers waiting to be discovered!
How many four digits numbers can be formed using 0123456789?
Assuming that the first digit of the 4 digit number cannot be 0, then there are 9 possible digits for the first of the four. Also assuming that each digit does not need to be unique, then the next three digits of the four can have 10 possible for each. That results in 9x10x10x10 = 9000 possible 4 digit numbers. If, however, you can not use the same number twice in completing the 4 digit number, and the first digit cannot be 0, then the result is 9x9x8x7 = 4536 possible 4 digit numbers. If the 4 digit number can start with 0, then there are 10,000 possible 4 digit numbers. If the 4 digit number can start with 0, and you cannot use any number twice, then the result is 10x9x8x7 = 5040 possilbe 4 digit numbers.
