we will assume that the can has a shape of a cylinder

let r = the radius of the circular top (the radius of the base of the cylinder)

h = 15 cm is the height of the cylinder

pi = 3.14 is a constant

the formula for the area of the cylinder is A = 2*(r^2)*pi + 2*r*pi*h

2*(r^2)*pi + 2*r*pi*h = 381

2*(r^2)*3.14 + 2*r*3.14*15 = 381

by solving the quadratic equation we find and consider the positive roots (the radius can not be negative number)

r = 3.31 cm

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the radius of the circular top is 3.31 cm.