Logo
    Logo

    Subject

    Quantitative Aptitude

    Topic

    Areas & Volumes

    A circular swimming pool is surrounded by a concrete wall 4ft wide. If the area of the concrete wall surrounding the pool is 11/25 that of the pool, then the radius of the pool is?

    ক)
    10ft
    খ)
    20ft
    গ)
    30ft
    ঘ)
    40ft

    Explanation

    let the radius of the pool be Rft Radius of the pool including the wall = (R+4)ft Area of the concrete wall = π[(R+4)2−R2]\mathrm\pi\left[\left(\mathrm R+4\right)^2-\mathrm R^2\right] = π[(R+4+R)(R+4−R)]  =  8π(R+2)\mathrm\pi\left[\left(\mathrm R+4+\mathrm R\right)\left(\mathrm R+4-\mathrm R\right)\right]\;=\;8\mathrm\pi\left(\mathrm R+2\right) sq feet => 8π(R+2)  =  1125πR2  =>11R2  =200(R+2)\mathrm\pi\left(\mathrm R+2\right)\;=\;\frac{11}{25}\mathrm{πR}^2\;=>11\mathrm R^{2\;}=200\left(\mathrm R+2\right) Radius of the pool R = 20ft

    Related questions

    The ratio between the length and the breadth of a rectangular park is 3 : If a man cycling along the boundary of the park at the speed of 12 km/hr completes one round in 8 minutes, then the area of the park (in sq. m) is:How many bricks, each measuring 25 cm x 25 cm x 6 cm, will be needed to build a wall of 8 m x 6 m x 5 cm?A large cube is formed from the material obtained by melting three smaller cubes of 3, 4 and 5 cm side. What is the ratio of the total surface areas of the smaller cubes and the large cube?A rectangular field is to be fenced on three sides leaving a side of 20 feet uncovered.If the area of the field is 680 sq.ft, how many feet of fencing will be required?A cistern of capacity 8000 litres measures externally 3 m by 6 m by 1 m and its walls are 5 cm thick. The thickness of the bottom is:The curved surface area of a cylindrical pillar is 264 m2and its volume is 924 m3. Find the ratio of its diameter to its height.A man walking at the speed of 4 kmph crosses a square field diagonally in 3 meters.The area of the field isA metallic sheet is of rectangular shape with dimensions 48 m x 36 m. From each of its corners, a square is cut off so as to make an open box. If the length of the square is 8 m, the volume of the box (in m3) is:

    Find Tutors

    View all Tutors