Question

A ap consist 50term and the 3rd term is 12 last term is 106 find its 20th term

Answer 1

Answer:

a20=80

Step-by-step explanation:

Answer 2

We know that ,

An= a + (n-1)×d

Given 3rd term is 12.

So, a3 = a + 2d

12 = a + 2d

a = 12 - 2d ------------ (1)

Given last term is 106 .

Last term = 50th term .

a50 = 106

Now , a50 = a + 49d

106 = a + 49d

a = 106 - 49d ----------- (2)

From equation (1) and (2) , we get

12 - 2d = 106 - 49d

-2d +49d = 106 - 12

47d = 94

d = 94 / 47

d = 2

By putting the value of d in equation (1), we get

a = 12 - 2d

a = 12 - 2 × 2

a = 12 - 4 = 8

=> a = 8

Now , we have to find 20th term ,

So , a20 = a + (n - 1)d

a20 = a + 19d

= 8 + 19 × 2

= 8 + 38

= 46

Hence , a20 is 46 .

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