JAMB Mathematics 2019 Objective — Question 21

Question 21 of 40 from the Joint Admissions and Matriculation Board (JAMB) Mathematics 2019 Objective paper, with the correct answer and a full explanation.

For what value of n is ⁿ⁺¹C₃ = 4(ⁿC₃)?

A. 4
B. 6
C. 3Correct
D. 5

Explanation

Expanding the combination formula and simplifying gives (n+1)/(n−2)=4 ⇒ n+1=4n−8 ⇒ 9=3n ⇒ n=3.

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