1. **Problem Statement:** Majo is covering a figure shaped like a triangular prism with glitter glue. The triangular face has sides 12 cm, 1 cm, and 13 cm. Each bottle of glue covers 20 square centimeters. We need to find how many bottles of glue Majo needs. 2. **Understanding the figure:** The triangular face is a right triangle (since $12^2 + 1^2 = 144 + 1 = 145$ and $13^2 = 169$, which is not equal, so we check if it is a right triangle by Pythagorean theorem: $12^2 + 5^2 = 144 + 25 = 169$, but 5 cm is not given, so we assume the triangle is right angled at the side 1 cm or 12 cm. However, since 13 cm is the longest side, it is likely the hypotenuse. 3. **Calculate the area of the triangular face:** Using Heron's formula: $$s = \frac{12 + 1 + 13}{2} = \frac{26}{2} = 13$$ $$\text{Area} = \sqrt{s(s - a)(s - b)(s - c)} = \sqrt{13(13 - 12)(13 - 1)(13 - 13)} = \sqrt{13 \times 1 \times 12 \times 0} = 0$$ This means the triangle is degenerate (area zero), so likely the triangle is right angled with sides 12, 5, 13 or 12, 1, 13 is a typo. Assuming the triangle is right angled with legs 12 cm and 1 cm: $$\text{Area} = \frac{1}{2} \times 12 \times 1 = 6 \text{ cm}^2$$ 4. **Calculate the surface area of the prism:** The prism has two triangular faces and three rectangular faces. - Area of two triangular faces: $2 \times 6 = 12$ cm$^2$ - The rectangular faces correspond to the sides of the triangle times the length of the prism (not given). Since length is not given, assume the prism length is 1 cm (or the problem is only about the triangular face). Since no length is given, we assume the problem asks only for the triangular face coverage. 5. **Calculate number of bottles needed:** Each bottle covers 20 cm$^2$. $$\text{Bottles} = \frac{\text{Area}}{20} = \frac{6}{20} = 0.3$$ Since bottles cannot be bought in fractions, Majo needs to buy 1 bottle. **Final answer:** Majo needs to purchase 1 bottle of glue.