If the number of 5-element subsets of the set A= a₁, a₂, , a₂₀ of 20 distinct elements is k times the number of 5-element subsets containing a₄ , then k is

Step-by-step solution

Set A= a₁, a₂, . ., a₂₀ has 20 distinct elements. We have to select 5-element subset. Number of 5-element subsets = ²⁰ C ₅ According to question aligned & ²⁰ C ₅= ( ¹⁹ C ₄ k . & 20 ! 5 ! 15 ! =k ( 19 ! 4 ! 15 ! ) & 20 5 =k k=4 aligned