How to do this question?

length of side of square = 8 cm

Step-by-step explanation:

Let's first find the area of the triangle, using the formula A = (1/2)(base)(height):

A = (1/2)(16 cm)(4 cm) = 32 cm^2.

Twice the area of the triangle would be 64 cm^2.

The area of the square is then 64 cm^2, which is the square of the length of one side of the square.  Taking the square root of 64 cm^2, we get

length of side of square = sqrt(64 cm^2) = 8 cm

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step-by-step explanation: