Question

find the 20th term of the AP whose 7th term is 24 less than its 11th term and first term is 12



please fast

Answer 1

let first term =a =12and common difference =d in an AP
nth term =an =a+(n-1)d ---(1)
7th term =a7=a+6d-----(2)
a11=a+10d----(3)
given
a11-a7=24
a+10d-(a+6d)=24
a+10d-a-6d=24
4d=24
d=6--(4)
required term =a20
=a+19d
=12+19*6
=12+114
=126

Answer 2

Answer :-

According to Question

a + 6d = a + 10d - 24

=> 4d = 24

=> d = 6

a = 12 (given)

Now

a20 = 12 + (20 - 1) 6

= 12 + 114

= 126

Thanks!!! :)