Mathematics 2022 JAMB Past Questions - Question 4: The sum of the first five terms 0f the series 4+2+1… is

Correct Answer

D

Explanation

To find the sum of the first five terms of the series 4 + 2 + 1 + ..., we need to determine the pattern or formula for the series. From the given terms, we can observe that each term is half of the previous term. The first term is 4, the second term is half of 4 (2), the third term is half of 2 (1), and so on. Using this pattern, we can write the general formula for the nth term of the series as:aₙ = 4 * (1/2)^(n-1)To find the sum of the first five terms, we can substitute the values of n from 1 to 5 into the formula and add them up:S₅ = a₁ + a₂ + a₃ + a₄ + a₅    = 4 * (1/2)^(1-1) + 4 * (1/2)^(2-1) + 4 * (1/2)^(3-1) + 4 * (1/2)^(4-1) + 4 * (1/2)^(5-1)    = 4 * 1 + 4 * (1/2) + 4 * (1/4) + 4 * (1/8) + 4 * (1/16)    = 4 + 2 + 1 + 1/2 + 1/4    = 8.75Therefore, the sum of the first five terms of the series 4 + 2 + 1 + ... is 8.75.