Questions
How many numbers lying between 10 and 1000 can be formed from the digits 1, 2, 3, 4, 5, 6, 7, 8, 9 (repetition of digits is allowed) ?
detailed solution
Correct option is B
Case I : When number in two digits.Total number of ways =9C1×9C1=9×9=81Case II : When number in three digits Total number of ways =9C1×9C1×9C1=9×9×9=729∴ Total number of ways = 81+ 729 =810Similar Questions
The number of ways in which we can get at least 6 successive tails when a coin is tossed 10 times in a row, is
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