Question

For A.P 21,18,15....... check which term is -27?

Answer 1

Step-by-step explanation:

Given -

AP = 21, 18, 15, ......

an = - 27

To Find -

Which term is - 27 ?

Now,

21, 18, 15, .......

here,

a = 21

d = 18 - 21 = - 3

an = - 27

Now,

• an = a + (n - 1)d

= - 27 = 21 + (n - 1)-3

= - 27 - 21 = - 3n + 3

= - 27 - 21 - 3 = - 3n

= - 51 = - 3n

= n = -51/-3

• = n = 17

Hence,

17th term of the AP is - 27.

Formula Used -

• an = a + (n - 1)d

Answer 2

Question :-

For A.P 21, 18, 15 ..... check which term is - 27..?

Given :-

here,

a = 21

d = 18 - 21 = - 3

an = - 27

Formula Used :-

an = a + ( n - 1 ) d

SoLuTiOn :-

=> an = a + ( n - 1) d

=> - 27 = 21 + ( n - 1) (-3)

=> - 27 = 21 - 3n + 3

=> - 27 - 21 - 3 = - 3n

=> - 51 = - 3n

=> 3n = 51

=> n = 51 /3

=> n = 17

${\purple{\boxed{\large{\bold{17th \:term \: of \:AP\: is\: - 27 }}}}}$