Answer: The radius is 5 units (approximately)
Step-by-step explanation: The area of a sector with central angle X is given as;
Area = (X/360) x pi x r^2
Since the area has been given as 15.71 units, we can input the known values into the formula as follows;
15.71 = (72/360) x 3.14 x r^2
By cross multiplication we now have
(15.71/3.14) = 1/5 x r^2
(15.71/3.14) x 5 = r^2
78.55/3.14 = r^2
25.0159 = r^2
Add the square root sign to both sides of the equation
5.001 = r
The radius is equal to 5 units (approximately)