JEE Mains · Maths · STD 11 - 6. permutation and combination
Number of \(4-\)digit numbers (the repetition of digits is allowed) which are made using the digits \(1, 2, 3\) and \(5\) , and are divisible by \(15\) , is equal to \(............\).
- A \(20\)
- B \(19\)
- C \(18\)
- D \(21\)
Answer & Solution
Correct Answer
(D) \(21\)
Step-by-step Solution
Detailed explanation
Sol. For number to be divisible by \(15\), last digit should be \(5\) and sum of digits must be divisible by \(3\).Possible combinations are
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