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How many even 3-digit numbers can be formed from the digits 1 2 5 6 9 if each digit can be used only once?
24 of them. So we have a 2 or 6 in the unit position, therefore (2)(4)(3) = 24 even three-digit numbers, can be formed.
How many 5 digit combinations for numbers 1- 25?
There are 9 1-digit numbers and 16-2 digit numbers. So a 5 digit combination is obtained as:Five 1-digit numbers and no 2-digit numbers: 126 combinationsThree 1-digit numbers and one 2-digit number: 1344 combinationsOne 1-digit numbers and two 2-digit numbers: 1080 combinationsThat makes a total of 2550 combinations. This scheme does not differentiate between {13, 24, 5} and {1, 2, 3, 4, 5}. Adjusting for that would complicate the calculation considerably and reduce the number of combinations.
How many 5 digit numbers can be formed out of 56789 if they can be repeated?
Five numbers (5, 6, 7, 8, 9) can be selected for each of the 5 digits. So, there are 5*5*5*5*5 or 55 or 3125 five digit numbers.
How many 3 digit numbers can be formed from the digits 357 with any digit repeated?
27 three digit numbers from the digits 3, 5, 7 including repetitions.
How many even numbers of four digits can be formed with digits 1 2 3 4 5 6 repetition of the digit is allowed?
6 x 6 x 6 x 3 = 648 6 because the first digit can be any of the numbers 6 again, because the second digit can be any of the numbers 6, again, because the third digit can be any of the numbers 3, because the fourth/last digit can only be 2, 4, or 6
