Question

If F (n) denotes the set of all divisions of n except 1, what is the least value of y satisfying [F(20) ∩ F (16) ⊆ F(y) ? 

(a) 1 

(b) 2 

(c) 4 

(d) 8

Answer 1

(c) 4

F (20) ∩ F (16) ⊆ F (y) 

⇒ [ { 2, 4, 5, 10, 20} ∩ { 2, 4, 8, 16}] ⊆ F (y) 

⇒ [{ 2, 4}] ⊆ F (y) 

∴ The least value of y is 4.