Question
Which term of the AP 72, 68, 64, 60, ..... is 0?
✓
Answer
In the given AP, we have a =72 and d = 68 - 72 = -4
Suppose there are n terms in given AP, we have
$T_n = 0$
$\Rightarrow a + (n - 1)d = 0$
$\Rightarrow 72 + (n - 1)(-4) = 0$
$\Rightarrow 72 - 4n + 4 = 0$
$\Rightarrow 4n = 76$
$\Rightarrow n = 19$
Hence, the $19^{th}$ term in the given AP is 0.
Suppose there are n terms in given AP, we have
$T_n = 0$
$\Rightarrow a + (n - 1)d = 0$
$\Rightarrow 72 + (n - 1)(-4) = 0$
$\Rightarrow 72 - 4n + 4 = 0$
$\Rightarrow 4n = 76$
$\Rightarrow n = 19$
Hence, the $19^{th}$ term in the given AP is 0.
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