What we know:
Shape is square
Area= 150 cm²
Area=s²
What we need to find: s=side of square
Area=s²
150=s²
√150=√s²
√150=s
s≈12 cm
C. 12cm
Remember when finding the square root of a number you get a positive and negative solution. In this case, length is positive so we do not need the negative solution.
