1) It is known that the interest ($I) received from an investment varies jointly as the interest rate per annum(r %) and the period of investment (T years). If an amount of money is invested obtained will be$1200.
(a) Express I in terms of r and T.
(b) If the same amount of money is invested for 3years and the interest rate is14% p.a., what will be the interest obtained
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2) The resistance (R units) of a metal wire varies inversely as the square of the diameter (d m) of the metal wire and directly as its length (l m). If the length of a metal wire is10m and its diameter is 4mm, then resistance is 75 units.
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(a) Express R in terms of d and l. (b) Find the resistance of a metal wire of length 40m and diameter 1 cm
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Answer : 1a) I = 50rT ; b) $2100 ; 2a) R = 3l / 25000d^2 ; b) 48 units