MCQ
Which term of the $ AP\ 25,20,15,-$ is the first negative term?
- A$10^{th}$
- B$9^{th}$
- C$8^{th}$
- ✓$7^{th}$
✓
Answer
Correct option: D.
$7^{th}$
$\text { Let } T_{n}<0 .$
Then $25+(n-1) \times(-5)<0$
$\therefore 30<5 n$
$\Rightarrow 5 n>30$
$\Rightarrow n>6$
So$,$ the required term is $7^{\text {th }}$.
Then $25+(n-1) \times(-5)<0$
$\therefore 30<5 n$
$\Rightarrow 5 n>30$
$\Rightarrow n>6$
So$,$ the required term is $7^{\text {th }}$.
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