WBJEE · Maths · Sequences and Series
Let \(d(n)\) denotes the number of divisors of \(n\) including 1 and itself. Then, \(d(225), d(1125)\) and \(d(640)\) are
- A in AP
- B in HP
- C in GP
- D consecutive integers
Answer & Solution
Correct Answer
(C) in GP
Step-by-step Solution
Detailed explanation
Here, \(225=3^{2} \times 5^{2}\) \(\Rightarrow d(225)=3 \times 3=9\) \(1126=3^{2} \times 5^{3}\) \(\Rightarrow \quad d(1125)=3 \times 4=12\) and \(640=2^{7} \times 5\) \(\Rightarrow \quad d(640)=8 \times 2=16\) Hence, 9,12 and 16 are in GP.
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