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Ex 13.2, 11 - The students of a Vidyalaya were asked - Ex 13.2

  1. Chapter 13 Class 9 Surface Areas and Volumes
  2. Serial order wise
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Ex 13.2, 11 The students of a Vidyalaya were asked to participate in a competition for making and decorating penholders in the shape of a cylinder with a base, using cardboard. Each penholder was to be of radius 3 cm and height 10.5 cm. The Vidyalaya was to supply the competitors with cardboard. If there were 35 competitors, how much cardboard was required to be bought for the competition?  [𝐴𝑠𝑠𝑢𝑚𝑒 𝜋= 22/7] Here the pen holder is open at the top, but covered at the bottom Surface area of 1 penholder = Curved Surface area of cylinder with + Area of bottom circle with radius 3 cm Radius (r) of the circular end of cylindrical penholder = 3 cm Height (h) of penholder = 10.5 cm Surface area of 1 penholder = Curved Surface area of cylinder with + Area of circle with radius 3 cm = 2πrh + πr2 = (2×22/7×3×10.5+22/7×(3)2) cm2 = (22/7 (2×3×10.5+(3)2)) cm2 = (22/7 (63+9)) cm2 = (22/7(72)) cm2 Area of cardboard required = Surface area of 35 penholder = 35 × (22/7 " × " 72) cm2 = 5 × (22" ×" 72) cm2 = 7920 cm2 Therefore, 7920 cm2 cardboard sheet will be bought.

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  • Rizwan Quraishi's image
    Rizwan Quraishi
    Nov. 26, 2017, 5:54 p.m.

    a cylindrical tank of height 1.4m and radius of the base is 56cm is made up of a thick metal sheet. How much metal sheet is required(Express in square meters)

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