Question

Find the 20th term from the last term of the AP:3.8.13. ...., 253.​

Answer 1

a=3,d=5,an=253

we know that:

an=a+(n-1)d

253=3+(n-1)5

253-3+5=5n

255=5n

n=51

now, t20=a+19d

= >3+95

=> 98

therefore,the 20th term of the AP is 98

Hope it helps u

Answer 2

hey,

there is a direct formula for this,

an= l- (n-1)d

where "l" is the last term of the AP,

hence,

here d=5,

an=253-(20-1)5

an=253-95

an=158

thanks❤