1. Radis of sphere r = 10.5 cm Surface area of sphere = 4πr² = 4 × 22/7 × 10.5 × 10.5 = 4 × 22 × 1.5 × 10.5 = 1386.00 cm² Hence, the surface area of sphere is 1386 cm²

    Radis of sphere r = 10.5 cm
    Surface area of sphere = 4πr²
    = 4 × 22/7 × 10.5 × 10.5 = 4 × 22 × 1.5 × 10.5 = 1386.00 cm²
    Hence, the surface area of sphere is 1386 cm²

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  2. Speed of river l = 2 Km/h = 2000 m/h, breadth b = 40 m and height h = 15 m Volume of water fall into the sea in 1 hour = lbh = 2000 × 40 × 3 = 240000 m³ So, volume of water fall into the sea in 1 minute = 240000m³/60 = 4000 m³ Hence, in 1 minute, 4000 m³ will fall into the sea.

    Speed of river l = 2 Km/h = 2000 m/h, breadth b = 40 m and height h = 15 m
    Volume of water fall into the sea in 1 hour = lbh = 2000 × 40 × 3 = 240000 m³
    So, volume of water fall into the sea in 1 minute = 240000m³/60 = 4000 m³
    Hence, in 1 minute, 4000 m³ will fall into the sea.

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  3. First case: Radius of balloon r = 7 cm Surface area of balloon = 4πr² = 4 × 22/7 × 7 × 7 = 4 × 22 × 7 = 616 cm² Hence, the surface area of ballon is 616 cm² Second case: Radius of balloon R = 14 cm Surface area of bolloon = 4πR² = 4 × 22/7 × 14 × 14 = 4 × 22 × 2 × 14 = 2464 cm² Hence, the surface arRead more

    First case:
    Radius of balloon r = 7 cm
    Surface area of balloon = 4πr²
    = 4 × 22/7 × 7 × 7 = 4 × 22 × 7 = 616 cm²
    Hence, the surface area of ballon is 616 cm²
    Second case:
    Radius of balloon R = 14 cm
    Surface area of bolloon = 4πR²
    = 4 × 22/7 × 14 × 14
    = 4 × 22 × 2 × 14
    = 2464 cm²
    Hence, the surface area of balloon is 2464 cm².
    Ratio of surface area = 616/2464 = 1/4
    Hence, the ratio of surface areas in two cases is 1:4

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  4. Length of water tank l = 6 m, breadth b = 5 m and height h = 4.5 m Volume of water tank = lbh = 6 × 5 × 4.5 = 135 cm³ = 135 × 1000 l = 135000 l Hence, the water tank can hold 135000 litres of water.

    Length of water tank l = 6 m, breadth b = 5 m and height h = 4.5 m
    Volume of water tank = lbh = 6 × 5 × 4.5 = 135 cm³ = 135 × 1000 l = 135000 l
    Hence, the water tank can hold 135000 litres of water.

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  5. Length of cuboidal vessel l = 10 m, breadth b = 8 m and volume V = 380 m³ Let, the heigth of cuboidal vessel = h m Volume of cuboidal vessel = lbh ⇒ 380 = 10 × 8 × h ⇒ h = 380/(10×8) = 4.75 m Hence, the height of cuboidal vessel be 4.75 m.

    Length of cuboidal vessel l = 10 m, breadth b = 8 m and volume V = 380 m³
    Let, the heigth of cuboidal vessel = h m
    Volume of cuboidal vessel = lbh
    ⇒ 380 = 10 × 8 × h
    ⇒ h = 380/(10×8) = 4.75 m
    Hence, the height of cuboidal vessel be 4.75 m.

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