Question

find the sum of first 20 term of an ap in which 11th term is 5 and 13 term is 79​

Answer 1

Answer:

Step-by-step explaination

The nth term of an A.P is

The 11th term is 5.

i.e. ....(1)

The 13th term is 79.

i.e. ....(2)

Subtract (1) from (2),

Substitute in (1),

The sum of n terms of an A.P is

The sum of first 20 terms of an A.P is

The sum of first 20 terms of an A.P is -270.

#Learn more

If 5^th and 6^th terms of an A.P are respectively 6 and 5. Find the 11^th term of the A.P

Answer 2

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