Considering all the possible conditions, 16,000 possible 7-digit telephone numbers that are multiples of 10
A permutation is an arrangement of a set of objects in a specific order.
If you want to calculate the number of permutations of a subset of n objects, you can use the following formula:
n! / (n - r)!
where r is the number of objects in the subset.
There are 8 options for the first digit of the telephone number (2, 3, 4, 5, 6, 7, 8, or 9) since the first digit cannot be 1. For each of the remaining 6 digits, there are 5 options (1, 3, 5, 7, or 9) since only odd digits may be used. Therefore, there are a total of 8 * 5^6 = 16,000 possible 7-digit telephone numbers.
To find the number of 7-digit telephone numbers that are multiples of 10, we can divide the total number of possible numbers by 10. Since 16,000 is not divisible by 10, we know that not all 7-digit telephone numbers are multiples of 10. However, we can divide 16,000 by 10 to find the number of groups of 10 numbers that can be formed: 16,000 / 10 = 1,600.
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