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  • Number of 4-digit numbers (the repeation of digits is allowed) which are made using the digits 1, 2, 3 and 5 , and are divisible by 15 , is equal toOption: 1</st

Number of 4-digit numbers (the repeation of digits is allowed) which are made using the digits 1, 2, 3 and 5 , and are divisible by 15 , is equal to

Option: 1

21


Option: 2

10


Option: 3

25


Option: 4

15


Answers (1)

best_answer
        

5

Last digit must be 5 and sum of digits is divisible by 3 for divisible by 15

Remaining 3 digits Arrange
(1, 1, 2) \frac{3 !}{2}=3 \\
(1, 3, 3) \frac{3 !}{2}=3 \\
(1, 5, 1) \frac{3 !}{2}=3 \\
(2, 2, 3) \frac{3 !}{2}=3 \\
(2, 3, 5) {3 !}=6 \\
(3, 5, 5) \frac{3 !}{2}=3 \\

Total numbers = 21

 

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