Question

Deva said .25th term from the last is 61 for the A.P.7,13,19, ......205. Verify it
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Answer 1

Answer:

Step-by-step explanation:

We have, l=61 and d= 13-7

6

25 term from end=l-(n-1)×d

61-(25-1)×6

61-(24)×6

61-144

-83

Answer 2

Answer:

The 25th term from the last is 61.

Step-by-step explanation:

The given AP is

7,13,19, ......205

We have to find the 25th term form the last. So, arrange the series in opposite order.

205, 198, .... , 19,13, 7

First term is 205. Common difference is

$d=7-13=-6$

The nth term of an AP is defined as

$a_n=a+(n-1)d$

$a_{25}=205+(25-1)(-6)$

$a_{25}=205+(24)(-6)$

$a_{25}=205-144$

$a_{25}=61$

Hence proved that the 25th term from the last is 61.