A telephone number consists of 7 digits. How many phone numbers are possible if the first digit is neither 7, 6, 5, 4, 3, 2, 1 nor 0? (Enter an exact number.)
A telephone number consists of 7 digits. How many phone numbers are possible if the first digit is neither 7, 6, 5, 4, 3, 2, 1 nor 0? (Enter an exact number.)
The formation of a telephone number is a significant use of counting. A telephone number consists of digits from 0 to 9. By different arrangements, different telephone numbers can be formed. It is an arrangement with repetition. In a telephone number, digits are allowed to repeat. The base of this formation is the fundamental principle of counting. When a work is done in n different ways and for each of these ways, another work can be performed in m different ways, together, the two works can be completed in different ways. Based on this fact, the formation of telephone numbers using 9 different digits is done.
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