Question
11, 8, 5, 2, . . . In this A.P. which term is number – 151?
✓
Answer
By, given A.P. 11, 8, 5, 2, . . .
we know that
a = 11, t1 = 8, t2 = 5
Thus, d = t2 – t1 = 5 – 8 = – 3
Given: tn = – 151
Now, By using nth term of an A.P. formula
tn = a + (n – 1)d
we can find value of “n”
Thus, on substituting all the value in formula we get,
– 151 = 11 + (n – 1)× ( – 3)
⇒ – 151 – 11 = (n – 1)× ( – 3)
⇒ – 162 = (n – 1) × ( – 3)
$\Rightarrow n -1=\frac{-162}{-3}=54$
⇒ n = 54 + 1 = 55
we know that
a = 11, t1 = 8, t2 = 5
Thus, d = t2 – t1 = 5 – 8 = – 3
Given: tn = – 151
Now, By using nth term of an A.P. formula
tn = a + (n – 1)d
we can find value of “n”
Thus, on substituting all the value in formula we get,
– 151 = 11 + (n – 1)× ( – 3)
⇒ – 151 – 11 = (n – 1)× ( – 3)
⇒ – 162 = (n – 1) × ( – 3)
$\Rightarrow n -1=\frac{-162}{-3}=54$
⇒ n = 54 + 1 = 55
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