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JAMB Mathematics 2017 Paper

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Question : 2

Total: 44

What is the next number in the series 2, 1,

\frac{1}{2}

\frac{1}{4}

...

$\frac{1}{3}$
$\frac{2}{8}$
$\frac{3}{7}$
$\frac{1}{8}$

Solution:

2, 1,

\frac{1}{2}

,

\frac{1}{4}

.....

There are 4 terms in the series

Therefore the next number will be the 5th term

T_n = 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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