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What is the next number in the series 2 1 frac ... - JAMB Mathematics 2017 Question

What is the next number in the series 2, 1, \(\frac{1}{2}\), \(\frac{1}{4}\)...
A
\(\frac{1}{3}\)
B
\(\frac{2}{8}\)
C
\(\frac{3}{7}\)
D
\(\frac{1}{8}\)
correct option: d
2, 1, \(\frac{1}{2}\), \(\frac{1}{4}\).....

There are 4 terms in the series
Therefore the next number will be the 5th term

Tn = ar\(^{n − 1}\) (formular for geometric series)

a = first term = 2

r = common rate = \(\frac{\text{next term}}{\text{previous term}}\) = \(\frac{1}{2}\)

n = number of terms

T5 = 5th term = ?

T5 = ar\(^{5 - 1}\)

= ar\(^4\)

= 2 × (ar\(^{n − 1}\))4

= 2 × \(\frac{1}{16}\)

= \(\frac{1}{8}\)
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