Question

Find the 9 th term from the end (towards the first term) of the A.P. 5, 9, 13, ...., 185.

Answer 1

Hey Mate
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Common difference, d, of the AP = 9 − 5 = 4 
Last term, l, of the AP = 185 
We know that the n th term from the end of an AP is given by l − ( n − 1) d. 
Thus, the 9 th term from the end is 
185 − (9 − 1)4 
= 185 − 4 × 8 
= 185 − 32 
= 153

Answer 2

Your answer !!

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d = 9 - 5 = 4

Now, the A. P will be reversed !

a9 = a + ( 9 - 1 ) d

a9 = 185 + 8 (4)

a9 = 185 + 32

a9 = 217

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