Question:
If the sum of three numbers in A.P. is 24 and their product is 440, find the numbers.
Solution:
Let the three numbers be $(a-d), a,(a+d)$.
Sum $=24$
$\Rightarrow(a-d)+a+(a+d)=24$
$\Rightarrow 3 a=24$
$\Rightarrow a=8 \quad \ldots(i)$
Product $=a(a-d)(a+d)=440$
$\Rightarrow a\left(a^{2}-d^{2}\right)=440$
$\Rightarrow 8\left(64-d^{2}\right)=440$ (From (i))
$\Rightarrow\left(64-d^{2}\right)=55$
$\Rightarrow d^{2}=9$
$\Rightarrow d=\pm 3$
With $\mathrm{a}=8, \mathrm{~d}=3$, we have :
$5,8,11$
With a $=8, \mathrm{~d}=-3$, we have:
$11,8,5$