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How many seven digit numbers contain the number seven at least once?
To find the total number of seven-digit numbers that contain the number seven at least once, we can use the principle of complementary counting. There are a total of 9,999,999 seven-digit numbers in total. To find the number of seven-digit numbers that do not contain the number seven, we can count the number of choices for each digit (excluding seven), which is 9 choices for each digit. Therefore, there are 9^7 seven-digit numbers that do not contain the number seven. Subtracting this from the total number of seven-digit numbers gives us the number of seven-digit numbers that contain the number seven at least once.
How many combinations are there if there are seven numbers and you have to have a four number combination?
That dependsThat depends upon whether you are allowed to repeat numbers. If you are allowed to repeat, that means that all seven digits (say 1 through 7) can be used in each of the four positions of your combination, even if a digit has been used in another position. That means there are 7 x 7 x 7 x 7 = 74 = 2401 possible combinations for your lock. But if you are not allowed to repeat, that means that every time you pick a digit for one spot, there will be one less digit for the next, and one less for the next, and so on. So, the first number can have seven possibilities, the second can have six, the third can have five, and the last can have four possible digits. That means there are 7 x 6 x 5 x 4 = 840 possible combinations for your lock, only about a third as many.Check out the related link at MathsIsFun. It has very good information on this subject.* * * * *That is true for PERMUTATIONS, but not for combinations. In a combination, the order of digits does not matter so that 1234 is the same as 1342 or 4213 ext.As a result you have 7C4 = 7!/[4!*(7-4)!] = 7*6*5/(3*2*1) = 35 combinations - not 2401.Incidentally, nCr is the notation for the number of combinations of r objects taken from n objects - exactly what the question asked for.
What is the whole number for seven billion?
The whole number for seven billion is 7,000,000,000. In numerical terms, this is represented by the digit 7 followed by nine zeros. This number is in the billions place value, indicating a quantity of seven billion units.
What is the tens place of 734?
The digit in the tens place of 734 is the 3. The number is pronounced seven three four.
Why are phone numbers seven digits long?
Phone numbers are seven digits long in some countries but differing lengths in others. It purely depends upon what number of phone numbers the country needs .
