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A letter lock consists of three rings ea...

A letter lock consists of three rings each marked with 10 different letters. No. of ways to make an unsuccessful attempts to open the lock is

A

899

B

999

C

479

D

568

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The correct Answer is:
B
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AAKASH SERIES-PERMUTATIONS & COMBINATIONS-EXERCISE-II
  1. 5 digit number divisible by 9 are to be formed by using the digits 0, ...

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  2. Number of numbers greater than 24000 can be formed by using digits 1, ...

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  3. A letter lock consists of three rings each marked with 10 different le...

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  4. The number of four digits telephone numbers having atleast one ...

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  5. The number of quadratic expressions with the coefficients drawn ...

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  6. Number of diffferent matrices that can be formed with elements 0, 1, 2...

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  7. Four dice are rolled then the number of possible out comes in which at...

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  8. Find the number of numbers less than 2000 that can be formed using the...

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  9. The number of odd numbers lying between 40000 and 70000 that can be ma...

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  10. Total number of four digit odd numbers that can be formed using 0, 1, ...

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  11. The number of numbers greater than 1000 but not greater than ...

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  12. Number of 5 digited numbers using 0,1,2,3,4 divisible by 4 with repeti...

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  13. Find the number of 4- digit numbers that can be formed using the digit...

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  14. Number of 4 digited numbers using 0, 1, 2, 3, 4, 5 divisible by 6 with...

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  15. The number of 5 digited numbers that contain 7 exactly once is

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  16. Number of different 6 digit numbers whose sum of digits to be odd is (...

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  17. The number of 5 letter words formed using the letters of DELHI begin a...

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  18. Number of bijections from Set-A containing n elements onto itself is 7...

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  19. Number of Surjections from Set - A containing n elements to the Set -B...

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  20. The number of ways in which 10 letters can be posted in 5 letter boxe...

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