Find the sum of the first $25$ terms of an AP whose $n^{t h}$ term is given by $a_{n}$ $= 2 - 3 n .$

- 925

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- 875

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- 950

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- 975

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Solution

The correct option is B $- 925$
Given, $a_{n} = 2 - 3 n$
$∴$ First term $= a = a_{1} = 2 - 3 = - 1$ and
Last term $= l = a_{25} = 2 - 3 \times 25 = - 73$
Now, $S_{25} = \frac{25}{2} [a + l]$
$= \frac{25}{2} [- 1 + (- 73)]$
$= 25 \times - 37 = - 925$

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Find the sum of the first 25 terms of an AP whose nth term is given by an =2−3n.

The correct option is B −925Given, an=2−3n∴ First term =a=a1=2−3=−1 andLast term =l=a25=2−3×25=−73Now, S25=252[a+l] =252[−1+(−73)] =25×−37=−925

Find the sum of the first $25$ terms of an AP whose $n^{t h}$ term is given by $a_{n}$ $= 2 - 3 n .$

The correct option is B $- 925$
Given, $a_{n} = 2 - 3 n$
$∴$ First term $= a = a_{1} = 2 - 3 = - 1$ and
Last term $= l = a_{25} = 2 - 3 \times 25 = - 73$
Now, $S_{25} = \frac{25}{2} [a + l]$
$= \frac{25}{2} [- 1 + (- 73)]$
$= 25 \times - 37 = - 925$