1. The distance between top and bottom rungs is 2(1/2)m and the distance between two successive rungs is 25 cm, therefore The number of rungs = 250/25 + 1 = 11 The lenght of rungs is increasing from 25 cm to 45 cm in the from of AP, whose first term a = 25 and the last term a₁₁ = 45 Let the common diffRead more

    The distance between top and bottom rungs is 2(1/2)m and the distance between two successive rungs is 25 cm, therefore
    The number of rungs = 250/25 + 1 = 11
    The lenght of rungs is increasing from 25 cm to 45 cm in the from of AP, whose first term a = 25 and the last term a₁₁ = 45
    Let the common difference of this AP be d.
    Therefore, a₁₁ = 45
    ⇒ a + (11 – 1)d = 45
    ⇒ 25 + 10d = 45
    ⇒ d = 20/10 = 2
    The lenght of wood required
    S₁₁ = 11/2[2a + (11 -1)d]
    = 11/2[2(25) + 10(2)]
    = 11 × 35 = 385 cm
    Hence, 385 cm lenght of the wood is required for the rungs.

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