Question

The 20th term of an AP whose 3rd term is 7 and the 7th term exceeds three times the third term by 2. Also find its nth term

Answer 1

let the first term of ap =a

let the common difference=d

given:

1.3rd term = 7

a+2d=7. ----(1)

2. 7th term exceeds the third term by two

a+6d= a+2d+2

4d = 2

d= 1/2

put the value of d in equation 1

a+2(1/2)= 7

a=6

20 th term = a+19d

6+19(1/2)= 6+9.5= 15.5

nth term = a+(n-1)d= 6+(n-1)1/2

= (11+n)/2

hope it helps you