Question

in an AP t15 -t11=12 find its common difference

Answer 1

t(15) - t(11) = 12

a + 14d - [ a + 10d] = 12

a + 14d - a - 10d = 12

14d - 10d = 12

4d = 12

d = 12/4

d = 3

Common difference = 3

I hope this will help you

(-:

Answer 2

Hey Nidhi,

Here is your solution :

Let ,

First term = a

Common difference = d.

Now,

⇒ nth term = First term + ( n - 1 ) common difference

⇒ 15th term = a + ( 15 - 1 )d

⇒ 15th term = a + 14d    ------- ( 1 )

Again,

⇒ nth term = First term + ( n - 1 )common difference 

⇒ 11th term = a + ( 11 - 1 )d

⇒ 11th term = a + 10d  --------- ( 2 ).

According to question,

⇒ 15th term - 11th term = 12

By substituting the value of ( 1 ) and ( 2 ),

⇒ a + 14d - ( a + 10d ) = 12

⇒ a + 14d - a - 10d = 12

⇒ 4d = 12

⇒ d = 12 ÷ 4

∴  d = 3.


The common difference is 3.

Hope it helps !!