JEE Mains · Maths · STD 11 - 6. permutation and combination
Let S denote the set of 4-digit numbers abcd such that \( a>b>c>d \) and P denote the set of 5-digit numbers having product of its digits equal to 20. Then \( n(S)+n(P) \) is equal to:
- A 210
- B 260
- C 50
- D 250
Answer & Solution
Correct Answer
(B) 260
Step-by-step Solution
Detailed explanation
For \(n ( s )={ }^{10} C _4=210\) \((5,4,1,1,1) \quad(5,2,2,1,1)\) For \(n(p)=\frac{5!}{3!}+\frac{5!}{2!2!}=50\) \(n(s)+n(p)=210+50=260\)
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