Question

Which term of the AP 5,13,21 and.......is 181

Answer 1

Answer:

a=5, d=8, an=181

an=a+(n-1)d

181=5+(n-1)8

181-5=(n-1)8

176/8=(n-1)

22=n-1

n=22+1

n=23

hope it helps u.....^_^

Answer 2

$\large\underline\pink{Given:-}$

• AP 5,13,21 and.......is 181

$\large\underline\pink{To find:-}$

• Fine the nth term of Ap is 181. ....?

$\large\underline\pink{Solutions:-}$

• first term = 5
• common difference = a2 - a1 = 13 - 5 = 8

an = a + (n - 1)d

an = nth terms = 181

a = first term = 5

n = number of term = ?

d = common difference = 8

181 = 5 + (n - 1) 8

181 = 5 + 8n -8

181 = 8n - 3

8n = 181 + 3

8n = 184

n = 23

hence the nth term is 3.

$\underline\mathfrak{Important \: \: formula:-}$

$\: \: \: \: \: {A_n} \: \leadsto \: a \: + \: {({n} \: - {1})} \: d$

$\: \: \: \: \: {S_n} \: \leadsto \: \frac{n}{2} \: {(a \: - \: l)}$

$\: \: \: \: \: {S_n} \: \: \leadsto \: \: \frac{n}{2} \: {[{2a} \: + {(n \: - \: {1})}]} \: d$

$\underline\mathfrak{more \: \: information:-}$

$\: \: \: \: \: \leadsto \: a \: \: = \: \: first \: \: terms$

$\: \: \: \: \: \leadsto \: d \: \: = \: \: common \: \: difference$

$\: \: \: \: \: \leadsto \: n \: \: = \: \: number \: \: of \: \: terms.$

$\: \: \: \: \: \leadsto \: l \: \: = \: \: last \: \: term$

$\: \: \: \: \: \leadsto \: {a_n} \: \: = \: \: nth \: \: term$