Jambmaths question:
The fifth term of AP is 24, and eleventh term is 96. Find the first term
Option A:
12
Option B:
4
Option C:
-12
Option D:
-24
Jamb Maths Solution:
$\begin{align} & {{T}_{n}}=a+(n-1)d \\ & {{T}_{5}}=a+4d=24----(i) \\ & {{T}_{11}}=a+10d=96---(ii)\, \\ & \text{Solving equation }(i)\text{ and }(ii) \\ & 6d=72 \\ & d=\frac{72}{6}=12 \\ & \text{Substituting }12\,\text{for }d\text{ in }(i) \\ & {{T}_{5}}=a+4(12)=24 \\ & a=24-48 \\ & a=-24 \\\end{align}$
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