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parth joshi

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  1. Asked: November 4, 2020In: Class 9

    Sides of a triangle are in the ratio of 12 : 17 : 25 and its perimeter is 540cm. Find its area.

    parth joshi
    Added an answer on March 15, 2023 at 9:16 am

    Perimeter of triangle = 540 cm The ratio of sides of triangle = 12: 17: 25 Let, one of the sides of triangle a = 12 x Therefore, remaining two sides are b = 17 x and c = 25x. We know that the perimeter of triangle = a + b + c ⇒ 540 = 12 x + 17 x + 25 x ⇒ 540 = 54x ⇒ x = 540/54 = 10 So, the sides ofRead more

    Perimeter of triangle = 540 cm
    The ratio of sides of triangle = 12: 17: 25
    Let, one of the sides of triangle a = 12 x
    Therefore, remaining two sides are b = 17 x and c = 25x.
    We know that the perimeter of triangle = a + b + c
    ⇒ 540 = 12 x + 17 x + 25 x
    ⇒ 540 = 54x
    ⇒ x = 540/54 = 10
    So, the sides of triangle are a = 12 × 10 = 120 cm, b = 17 × 10 = 170 cm and c = 25 × 10 = 250 cm.
    So, the semi- perimeter of triangle is given by
    S = (a + b + c /2) = 540/2 = 270 cm
    Therefore, using Heron’s formula, the area of triangle = √s(s – a)(s – b)(s – c)
    = √270(270 – 120)(270 – 170)(270 – 250)
    = √270(150)(100)(20)
    = √81000000
    = 9000 cm²
    Hence, the area of triangle is 9000 cm².

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  2. Asked: November 4, 2020In: Class 9

    An isosceles triangle has perimeter 30 cm and each of the equal sides is 12 cm. Find the area of the triangle.

    parth joshi
    Added an answer on March 15, 2023 at 9:16 am

    Perimeter of triangle = 30 cm Two sides of triangle b = 12 cm and c = 12 cm. Let, the third side = a cm We know that the Parimeter of triangle = a + b + c ⇒ 30 = a + 12 + 12 ⇒ 30 - 24 = a ⇒ a = 6 So, the Semi- perimeter of triangle is given by S = a + b + c /2 = 30/2 = 15 cm Therefore, using Heron'sRead more

    Perimeter of triangle = 30 cm
    Two sides of triangle b = 12 cm and c = 12 cm.
    Let, the third side = a cm
    We know that the Parimeter of triangle = a + b + c
    ⇒ 30 = a + 12 + 12
    ⇒ 30 – 24 = a
    ⇒ a = 6
    So, the Semi- perimeter of triangle is given by
    S = a + b + c /2 = 30/2 = 15 cm
    Therefore, using Heron’s formula, the area of triangle = √s(s – a)(s – b)(s – c)
    = √15(15 -6)(15 -12)(15 -12)
    = √15(9)(3)(3)
    = 9√15 cm²
    Hence, the area of triangle is 9√15 cm².

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  3. Asked: November 4, 2020In: Class 9

    A capsule of medicine is in the shape of a sphere of diameter 3.5 mm. How much medicine (in mm³) is needed to fill this capsule?

    parth joshi
    Added an answer on March 14, 2023 at 11:34 am

    Radius of capsule r = 3.5/2 = 1.75 mm Volume of medicine to fill the capsule = = 4/3πr³ = 4/3 × 22/7 × 1.75 × 1.75 × 1.75 = 4/3 × 22 × 0.25 × 1.75 × 1.75 = 22.46 mm³ (approx) Hence, 22.46 mm³ medicine is required to fill this capsule.

    Radius of capsule r = 3.5/2 = 1.75 mm
    Volume of medicine to fill the capsule = = 4/3πr³
    = 4/3 × 22/7 × 1.75 × 1.75 × 1.75
    = 4/3 × 22 × 0.25 × 1.75 × 1.75
    = 22.46 mm³ (approx)
    Hence, 22.46 mm³ medicine is required to fill this capsule.

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  4. Asked: November 5, 2020In: Class 9

    Find the volume of a sphere whose surface area is 154 cm².

    parth joshi
    Added an answer on March 14, 2023 at 11:20 am

    Surface area of sphere A = 154 cm² Let, the radius of sphere = r cm We know that the surface area of sphere = 4πr² ⇒ 154 = 4 × 22/7 × r² ⇒ r² = (154 × 7)/(22×4) = 49/4 ⇒ r = √49/4 = 7/2 Volume of sphere = 4/2πr³ = 4/3 × 22/7 × (7/2)³ = 4/3 × 22/7 × 7/2 × 7/2 × 7/2 = 539/3 = 179(2/3) cm³ Hence the voRead more

    Surface area of sphere A = 154 cm²
    Let, the radius of sphere = r cm
    We know that the surface area of sphere = 4πr²
    ⇒ 154 = 4 × 22/7 × r²
    ⇒ r² = (154 × 7)/(22×4) = 49/4
    ⇒ r = √49/4 = 7/2
    Volume of sphere = 4/2πr³
    = 4/3 × 22/7 × (7/2)³
    = 4/3 × 22/7 × 7/2 × 7/2 × 7/2
    = 539/3 = 179(2/3) cm³
    Hence the volume of sphere is 179(2/3) cm³.

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  5. Asked: November 4, 2020In: Class 9

    A dome of a building is in the form of a hemisphere. From inside, it was white-washed at the cost of Rs 498.96. If the cost of white-washing is Rs 2.00 per square metre, find the

    parth joshi
    Added an answer on March 14, 2023 at 11:19 am

    Let the internal radius of dome = r m Internal surface area of dome = 2πr² cost of white washing at the rate of Rs 2 = 2πr² × Rs 2 = Rs 4πr² ⇒ Rs 4πr = Rs 498.96 ⇒ 4 × 22/7 × r² = 498.96 ⇒ r² = (498.96×7)/4×22) = 39.69 ⇒ r = √39.69 = 6.3 m Therefore, the internal surface of dome = 2πr² = 2 × 22/7 ×Read more

    Let the internal radius of dome = r m
    Internal surface area of dome = 2πr²
    cost of white washing at the rate of Rs 2 = 2πr² × Rs 2 = Rs 4πr²
    ⇒ Rs 4πr = Rs 498.96
    ⇒ 4 × 22/7 × r² = 498.96
    ⇒ r² = (498.96×7)/4×22) = 39.69
    ⇒ r = √39.69 = 6.3 m
    Therefore, the internal surface of dome = 2πr²
    = 2 × 22/7 × (6.3)2
    = 2 × 22/7 × 6.3 × 6.3
    = 2 × 22 × 0.9 × 6.3
    = 249.98 m²
    Hence, the inside surface area of the dome is 249.48 m².
    (II) Volume of the air inside the dome = 2/3πr³
    = 2/3 × 22/7 × (6.3)³
    = 2/3 × 22/7 × 6.3 × 6.3 × 6.3
    = 2 × 22 × 0.3 × 6.3 × 6.3
    = 523.9 cm³
    Hence, the volume of the air inside the dome is 523.9 cm³.

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