I was also at first confused, and I find the problem as published in 1894 (i.e. almost 130 years ago) much clearer: "A circle containing one acre is cut by ano

I was also at first confused, and I find the problem as published in 1894 (i.e. almost 130 years ago) much clearer: "A circle containing one acre is cut by another whose centre is on the circumference of the given circle, and the area common to both is one-half acre. Find that radius of the cutting circle." I think that formulation had to be at least mentioned near the beginning of the text, when not used in the first sentence.