Question 35 of 42intermediate🔧 ApplyNumerical4 marks

Find r if (i) ⁵Pᵣ = 2⁶Pᵣ₋₁ (ii) ⁵Pᵣ = ⁶Pᵣ₋₁.

(i)
Answer

r = 3

(ii)
Answer

r = 4

Explanation

This question involves solving permutation equations using the formula ⁿPᵣ = n!/(n-r)!. The key is to expand both sides using factorial notation, cancel common terms, and solve the resulting quadratic equation. For both parts, we must ensure r \leq 5 since we have ⁵Pᵣ, and r \geq 1 for the permutation to be valid.