Question

Find the 20th term if AP is 3;5;7;9

Answer 1

Step-by-step explanation:

a = 3

d = 2

n = 20

an = a + ( n-1 ) d

= 3 + ( 20 - 1 ) 2

= 3 + (19)2

= 3 + 38

= 41

Answer 2

$\blue{\bold{\underline{\underline{Answer:}}}}$

$\green{\tt{\therefore{20th\:term=41}}}$

$\orange{\bold{\underline{\underline{Step-by-step\:explanation:}}}}$

$\green{\underline \bold{Given: }} \\ \tt: \implies A.P = 3,5,7,9 \\ \\ \red{\underline \bold{To \: Find: }} \\ \tt: \implies 20th \: term \:of \: this \: A.P(a_{20}) = ?$

• According to given question :

$\green{\tt: \implies First \: term = 3} \\ \\ \tt:\implies Common \: difference = a_{2} - a_{1} \\ \\ \tt:\implies Common \: difference =5 - 3 \\ \\ \green{\tt: \implies Common \: difference =2} \\ \\ \tt: \implies Number \: of \: terms = 20 \\ \\ \bold{As \:we \: know \: that} \\ \tt: \implies a_{n} = a +( n - 1)d \\ \\ \text{Putting \: given \: value } \\ \tt: \implies a_{20} = 3 + (20 - 1) \times 2 \\ \\ \tt: \implies a_{20} =3 + 19 \times 2 \\ \\ \tt: \implies a_{20} =3 + 38 \\ \\ \green{\tt: \implies a_{20} =41}$