Neco Model Questions Vol1 2019 Mathematics Question 20

Practice objective / multiple choice question 20 from the 2019 Neco Model Questions Vol1 Mathematics examination.

Neco Model Questions Vol1 2019 Mathematics Objective / Multiple Choice Medium Difficulty
Question 20 NECO_MODEL_QUESTIONS_VOL1 • 2019 • MATHEMATICS • objective

Let \(S_n = \displaystyle\sum_{k=1}^{n} k\cdot 2^{k}\). (a) Derive a closed‑form expression for \(S_n\) in terms of \(n\). (b) Using the expression, compute \(S_5\).

Answer Options

A. S_n = 2 - (n+1)2^{n} + n2^{n+1}; S_5 = 130
Correct Answer B. S_n = 2 - (n+1)2^{n+1} + n2^{n+2}; S_5 = 258
C. S_n = 2 - (n+2)2^{n+1} + n2^{n+2}; S_5 = 254
D. S_n = (n-1)2^{n+2} - (n+2)2^{n+1} + 2; S_5 = 300
Correct Answer
B
Correct Option:
S_n = 2 - (n+1)2^{n+1} + n2^{n+2}; S_5 = 258

About This Question

This is Neco Model Questions Vol1 2019 Mathematics Question 20. It is one of the objective questions from the 2019 Neco Model Questions Vol1 Mathematics examination.

Difficulty level: Medium .

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