The length and breadth of a cuboidal store are in the ratio 2 : 1 and its height is 3.5 metres. If the area of its four walls (including doors) is 210 m$$^2$$, then its volume is

Let the length of breadth of the cuboidal store be 2x and x respectively.

Area of its four walls = 2(length $$\times$$ height) + 2(breadth $$\times$$ height)

210 = 2(2x $$\times$$ 3.5) + 2(x $$\times$$ 3.5)

7x + 14x = 210

x = 10

Length of the cuboidal store = 2x = 2 $$\times$$ 10 = 20

Breadth of the cuboidal store = x =10

Volume of store = length $$\times$$ breadth $$\times$$ height = 20 $$\times$$ 10 $$\times$$ 3.5 = 700 m$$^2$$