$4$ kg of rice at ' $5$ per kg is mixed with $8$ kg of rice at ` $6$ per kg. Find the average price of the mixture.
Then, by the unitary method:
$n_1 + n_2$ corresponds to $A_2 – A_1$
$\rightarrow 1 + 2$ corresponds to $6 – 5$
That is, $3$ corresponds to $1$
$\therefore n_2$ will correspond to $\dfrac{(A_2 - A_1)n_2}{(n_1 +n_2 )} $
In this case $\frac{1}{3} \cdot 2 = 0.66$. Hence, the required answer is $5.66$.
My doubt is that I don't understand this solution given in my book, I'm stuck at how $n_2$ will correspond to $\dfrac{(A_2 - A_1)n_2}{n_1 + n_2}$.
PS: Here $A_2$ and $A_1$ are $6$ and $5$, I will attach the reference If you don't understand the terminologies, This is a basic question in Alligation and Mixture.