Question

which term of the A.P
18,15/1/2,13....is-47?
​

Answer 1

Answer :

$\boxed{\bf{\star\:\: a_{28}\:=\:(-47)\:\:\star}}$

Correct Question :–

Which Term of the A.P. 18 , 15.5 , 13 , ... is (-47) ?

Explanation :

Given :–

• A.P.  :- 18 , 15.5 , 13 ,...
• where a = 18 , d = (-2.5) , aₙ = (-47) .

To Find :–

• aₙ = (-47) where we have to find the nth term .

Formula Applied :–

• $\boxed{\sf{\star\:\:a_n\:=\:a\:+\:(n\:-\:1)d\:\:\star}}$

Solution :–

We have , a = 18 , d = (-2.5) and aₙ = (-47) .

Putting these values in the formula $\sf{a_n\:=\:a\:+\:(n\:-\:1)d}$ .

$\rightarrow \sf{(-47)\:=\:18\:+(n\:-\:1)(-2.5)}$

$\rightarrow \sf{(-47)\:-\:18\:=\:(n\:-\:1)(-2.5)}$

$\rightarrow \sf{(-67.5)\:=\:(n\:-\:1)(-2.5)}$

$\rightarrow \sf{\dfrac{(-67.5)}{(-2.5)} \:=\:(n\:-\:1)}$

$\rightarrow \sf{27\:=\:(n\:-\:1)}$

$\rightarrow \:\sf{n\:=\:27\:+\:1}$

$\rightarrow \:\boxed{\sf{n\:=\:28}}$

∴ The 28th Term of the A.P. is (-47) .