1. **Problem statement:** We need to find the cost of cementing the inside walls and base of a cylindrical water tank with an internal radius of 2.5 m and depth 4 m, at a rate of 60 per square meter. 2. **Formula used:** The surface area to be cemented includes the curved surface area and the base area of the cylinder. - Curved surface area (CSA) = $$2\pi rh$$ - Base area = $$\pi r^2$$ - Total area = CSA + Base area = $$2\pi rh + \pi r^2$$ 3. **Substitute values:** - Radius $$r = 2.5$$ m - Height $$h = 4$$ m 4. **Calculate curved surface area:** $$2 \times \pi \times 2.5 \times 4 = 20\pi$$ square meters 5. **Calculate base area:** $$\pi \times (2.5)^2 = 6.25\pi$$ square meters 6. **Calculate total area:** $$20\pi + 6.25\pi = 26.25\pi$$ square meters 7. **Approximate total area:** Using $$\pi \approx 3.1416$$, $$26.25 \times 3.1416 = 82.466$$ square meters 8. **Calculate cost:** Cost = Area $$\times$$ rate = $$82.466 \times 60 = 4947.96$$ **Final answer:** The cost of cementing the walls and base is approximately 4948.