Q13 of 67 Page 195

From a wax cuboid of dimensions 11 cm × 3.5 cm × 2.5 cm, a candle of diameter 2.8 cm is made. Find the length of the candle.

Length of wax cuboid = l = 11 cm


Breadth of wax cuboid = b = 3.5 cm = cm


Height of wax cuboid = h = 2.5 cm = cm


Diameter of candle = 2.8 cm


Radius of candle = r = = 1.4 cm


Let the length of candle be l1


The candle is cylindrical so the length of candle will be its height


Candle is made from wax cuboid hence volume of cuboid wax is equal to volume of cylindrical candle candle


Volume of wax cuboid = lbh


Volume of cylindrical candle = πr2l1


⇒ lbh = πr2l1


⇒ 11 × × = × 1.42 × l1


⇒ × = 2 × 0.2 × 1.4 × l1


⇒ × = 0.56 × l1


⇒ × = 0.08 × l1


⇒ × = × l1


⇒ l1 =


⇒ l1 =


⇒ l1 =


⇒ l1 = 15.625 cm


Therefore, candle is 15.625 cm long


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