from typing import Tuple


class Inertia:
    def __init__(self, area: float, centroid: Tuple[float, float]):
        self.area = area
        self.centroid = centroid

    def __add__(self, other):
        AX = self.area * self.centroid[0] + other.area * other.centroid[0]
        AY = self.area * self.centroid[1] + other.area * other.centroid[1]
        self.area = self.area + other.area
        self.centroid = (AX / self.area, AY / self.area)