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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