Q. 64.2( 196 Votes )
Check whether – 150 is a term of the AP : 11, 8, 5, 2 . . .
To find: Whether -150 is term of the AP
Given: a = 11, d = 8 – 11 = - 3, an = - 150, n = ?
We know that an = a + (n – 1)d
a = first terms of AP
n = no. of terms of AP
d = common difference of AP
Applying the formula, we get
Or, - 150 = 11 + (n – 1)(- 3)
Or, (n – 1)(-3) = - 150 – 11 = - 161
Or, n – 1 = 161/3
n - 1 = 53.67
It is clear that 161 is not divisible by three and we shall get a fraction as a result. But number of term cannot be a fraction.
Hence, - 150 is not a term of the given AP.
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