Q. |
How many 7 digit telephone numbers can be constructed if each number starts with 91 and no digit appears more than once? |
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A. 1680 |
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B. 6720 |
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C. 3360 |
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D. 13440 |
If each number starts with 91,
Remaining digits left = 8 (Out of 10 digits)
And remaining places left = 5
So total numbers = 8 × 7 × 6 × 5 × 4 = 6720