Question

ww7. Find the 31st term of an AP whose 11th term is 38 and the 16th tern
18,
1
6. Check whether - 150 is a term of the AP: 11, 8, 5,2...
13,...,
2
8. An AP consists of 50 terms of which 3rd term is 12 and the last to
term​

Answer 1

Answer:

a31 = ?

11th term is 38

a11 = 38

a+10d = 38             ...........           (1)

16th term = 18

a16 = 18

a+15d = 38             ...........           (2)

subtracting  (2) from  (1)

a+10d = 38  

a+15d = 18  

-  -          -

-----------------

-5d = 20

d = -20/5

d= - 4

putting d= - 4 in (2)

a+15d = 18  

a+15 x (-4) = 18

a-60 = 18

a= 18+60

a=78

Now,

a31 = a+30d

     =78+30 x (-4)

     =78-120

     =  42

a31= 42