The problem asks to find the radius R of the circular arc forming the upper part of the stove's casing. The diagram shows that the width of the casing is 64 cm and the height to the start of the arc is 60 cm. The arc is centered in the middle of the lower part of the casing.
Let the center of the arc be at point O. The distance from the center to the sides of the casing is 64/2 = 32 cm. The distance from the center to the bottom of the arc is R. The height from the bottom of the casing to the start of the arc is 60 cm. Therefore, the vertical distance from the center of the arc to the bottom of the casing is R. The vertical distance from the center of the arc to the top of the casing is R - 60.
Using the Pythagorean theorem, we have R^2 = 32^2 + (R-60)^2. Solving for R: R^2 = 1024 + R^2 - 120R + 3600. This simplifies to 120R = 4624, so R = 4624 / 120 = 38.53 cm.