2020 · Q19
Let d(n) denote the number of positive divisors of a positive integer n. Which of the following are correct?
- 1d(5) = d(11)
- 2d(5)⋅d(11) = d(55)
- 3d(5) + d(11) = d(16)
Select the correct answer using the code given below:
Elementary MathematicsNumber System
- A1 and 3 only
- B1 and 2 only
- C2 and 3 only
- D1, 2 and 3
Explanation
d(5) = d(11) = 2, so statement 1 is true. d(55) = 4 = 2*2, so statement 2 is true. But d(16) = 5 while d(5)+d(11) = 4, so statement 3 is false. Statements 1 and 2 only - option (B).