Question

Sum $3.75,3.5,3.25$, ..... to $16$ terms.

Answer 1

The given series is $3.75,3.5,3.25,...$ to $16$ terms

$\therefore a=3.75$

and $d=(3.5-3.75)=-0.25$

$\therefore S_n=2a+(n-1)d$

$⟹S_{16}=2\times 3.75+[(16-1)\times (-0.25)]$

$=7.5+(-3.75)$

$S_{16}=3.75$