9. Given:
$$
\text { Profit margin of goods }=\frac{\text { Selling price of goods }- \text { Cost price of goods }}{\text { Cost price of goods }} \text {. }
$$

A merchant operates two types of goods, A and B. The profit margin of each piece of good A is $40 \%$, and the profit margin of each piece of good B is $60 \%$. When the number of pieces of good B sold is $50 \%$ more than the number of pieces of good A sold, the merchant's total profit margin is $50 \%$. Then, when the number of pieces of goods A and B sold are equal, the total profit margin the merchant gets is . $\qquad$
$9.48 \%$.
Let the purchase price of item A be $a$ yuan, then the selling price is $1.4 a$ yuan;
the purchase price of item B be $b$ yuan, then the selling price is $1.6 b$ yuan.
Assume item A is sold $x$ units, then item B is sold $\frac{3}{2} x$ units. Set up the equation
$$
\frac{0.4 a x+0.6 b \times \frac{3}{2} x}{a x+\frac{3}{2} b x}=0.5 \text {. }
$$

Solving for $a=\frac{3}{2} b$.
Therefore, when both item A and item B are sold $y$ units, the total profit is
$$
\frac{0.4 a y+0.6 b y}{a y+b y}=\frac{0.4 a+0.6 b}{a+b}=48 \% .
$$