Question
Question: If \(n + 2C_{8}:^{n - 2}P_{4} = 57\):16, then n is equal to...
If n+2C8:n−2P4=57:16, then n is equal to
A
19
B
18
C
17
D
20
Answer
19
Explanation
Solution
Given
∠n+2−86mu∠8∠n+26mux6mu∠n−2∠n−2−46mu=6mu1657
⇒ ∠n−2∠n+26mu=6mu∠86mux6mu1657
⇒ (n+2) (n+1) n (n – 1)
= 168x7x6x5x4x3x2x57
= 7 x 6 x 5 x 4 x 3 x 19 x 3
= (7 x3) (5 x 4) (19) (6 x 3)
= 21 x 20 x 19 x 18
⇒ n = 19 (By inspection)