Question

A=-18.9,d=2.5,an=3.6,n=?

Answer 1

Answer:n=10

Step-by-step explanation:

since the formula is an=A+(n-1)*d

(3.6+18.9)/2.5=n-1

9=n-1

n=10

Answer 2

Answer:-

$\small\sf{a=-18.9}$

$\small\sf{d=2.5}$

$\small\sf{an=3.6}$

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$\small\sf{So\:putting\:the\:values}$

$\small\sf{an=a+(n-1)d}$

$\small\sf{3.6=-18.9+(n-1)(2.5)}$

$\small\sf{3.6=-18.9+2.5n-2.5}$

$\small\sf{2.5n=3.6+21.4}$

$\small\sf{2.5n=25.0}$

$\small\sf{n=10}$