Question

find the value of a30-a20 of the Ap 3,8,13,18______

Answer 1

Solution :

We need to find $a_{30} - a_{20} = ?$

So, here d = 8 - 3 = 13 - 8 = 5

a = 3

At first, let me find $a_{30}$ ,

Here , n = 30 ,

Formula ⇒ $a_{n} = a + ( n -1 ) d$

Therefore, $a_{30} = 3 + ( 30 - 1 ) 5 \\\\a_{30} = 3 + 145 \\\\a_{30} = 148 ...... (1)$

Now, let me find $a_{20} = ?$

Here , n = 20

So , $a_{20} = 3 + ( 20 - 1 ) 5 \\ \\a_{20} = 3 + 95 \\ \\ a_{20} = 98 ....(2)$

From (1) & (2) , we got values of $a_{30}$ & $a_{20}$

So now,

$a_{30} - a_{20} =$ 148 - 98 = 50