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The `5^(th` term of an AP is 82 and the `12^(th` term is 103.
Find:
(i)the first term and common difference
(ii)the sum of the first 21 terms.
(b) A staircase was built such that each
subsequent stair has a uniform difference in height.The height of the `6^(th` stair from the horizontal floor was 85 cm and the height of the `10^(th` stair was 145 cm.Calculate the height of the `1^(st` and
the uniform difference in height of the stairs.
(c) During the construction of the staircase,each step was supported by a vertical piece of timber.If the staircase has 11
stairs ,calculate the total length of the timber used.