Don't get confused by the "0.01 cm" that's just telling you to round to the hundredths place. Moving on, the shaded area's exterior shows us that it is a square. Meaning you do s^2 to find the area. So, you find the square root of 15 which is 3.87... This means the diameter is also 3.87 because the diameter is equivalent to the side's measurement. Divide 3.87 by 2 to find the radius, giving you 1.935. This represents OT's length. Now, just round to the hundredths giving you 1.94 cm.
