Q8 of 176 Page 8

Find the 8th term from end of the A.P. 7, 10, 13, ..., 184.

Here, a = 7, d = 10 – 7 = 3 and l = 184


where l = a + (n – 1)d


Now, to find the 8th term from the end, we will find the total number of terms in the AP.


So, 184 = 7 + (n – 1)(3)


184 = 7 + 3n – 3


184 = 4 + 3n


180 = 3n


n = 60


So, there are 60 terms in the given AP.


Last term = 60th


Second last term = 60 – 1 = 59th


Third last term = 60 – 2 = 58th


And so, on


So, the 8th term from the end = 60 – 7 = 53th term


So, an = a + (n – 1)d


a53 = 7 + (53 – 1)(3)


a53 = 7 + 52 × 3


a53 = 7 + 156


a53 = 163


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